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• How can I improve the performance of a Northstar exhaust system?

• Road Sensing Suspension System

• How Often Should I Change My Oil? The GM Oil Life System

• Next-Generation Northstar Sets New Standard

• Cadillac Recommended Maintenance Schedule*

• Northstar Maintenance / Tune up

• Northstar Oil Consumption

• Transmission Flushing - Good or bad?

• Camel Mode - Loss of Coolant Protection

• Transmission Fluid Information

• Changing Coolant and Using the Correct Number of Tablets

• Warming-Up Your Cadillac's Northstar Properly

• Several Ways to Check for a Blown Head Gasket

• Occasional Full-Throttle Acceleration Is Good For Your Engine

• 2002 Escalade - How do I Disable Daytime Running Lights (DRLs)

• 2002 Escalade - How do I Reset the Oil Life Indicator

Cadillac Recommended Maintenance Schedule (back to the top)

"A" Service - 3k $59.95 (price in New York) - Every 3000 miles
- Change engine oil, lube and filter (additional charge for Northstar)
- Reset oil life indicator
- Lubricate chassis, rubber bushings and hinges
- Inspect air filter
- Check tire inflation
- Visual inspection of tire wear
- Visual inspection of wheel alignment
- Check all instruments, accessories and lights
- Check and fill all fluid levels

"B" Service - 6k $109.95 (price in New York) - Every 6000 - 21000 - 36000 - 51000 - 66000 - 81000 miles
- Change engine oil, lube and filter (additional charge for Northstar)
- Rotate tires - computerized state of the art vibration system
- Inspect front suspension and check wheel alignment
- Lubricate and inspect front suspension, drive line, steering, hinges, cable guides and contact points (if applicable)
- Inspect front disc brake system
- Inspect rear brake system
- Inspect drive belts, hoses, cables, lights, horn, filters, tires and fluid levels
- Inspect exhaust system and heat shields for leaks, damage or loose parts
- Inspect throttle linkage
- Torque carburetor or throttle body mounting bolts (6000 miles only)
- Bravada rear axle service, drain and flush rear axle and refill fluid (Add $99.95 (price in New York))

"C" Service - 15k $329.95 (price in New York) - Every 15000 - 45000 - 75000 - 105000 miles
- Change engine oil, lube and filter (additional charge for Northstar)
- Replace air filter, fuel filter and PCV
- Check belts and hoses
- Lubricate and inspect front suspension, drive line, steering, hinges, cable guides and contact points (if applicable)
- Clean, inspect front disc brake system
- Clean, inspect rear brake system
- Inspect parking brake for damage and operation (adjust if needed)
- Inspect exhaust system and heat shields for leaks, damage or loose parts
- Rotate tires and balance - computerized state of the art vibration system
- Inspect front suspension and check wheel alignment
- Service automatic transmission/transaxle, replace necessary fluid and pan gasket, clean filter screen
- Service battery - Test battery charge and clean terminals
- Road test vehicle
- Wash and vacuum (Saturday only coupon offer**)
- Throttle body and fuel injection cleaning (Add $99.95 (price in New York))
- Bravada rear axle service, drain and flush rear axle and refill fluid (Add $99.95 (price in New York))
- Timing belt replacement (Catera only - additional parts not included) (Add $289.95 (price in New York))

"D" Service - 30k $459.95 (price in New York) - Every 30000 - 60000 - 90000 - 120000 miles
- Change oil, lube and filter (additional charge for Northstar)
- Replace air cleaner and PCV, fuel filter
- Replace engine coolant, tighten hoses and connections, pressure test (2 gallons)
- Service automatic transmission/transaxle, replace necessary fluid and pan gasket, clean filter screen
- Inspect exhaust system and heat shields for leaks, damage or loose parts
- Reset oil light indicator
- Lubricate body hinges and latches
- Service throttle body, remove carbon deposits, set idle to factory specifications, add fuel additive
- Inspect front suspension and check wheel alignment
- Tire rotation and balance - computerized state of the art vibration system
- Clean, inspect front disc brake system
- Clean, inspect and adjust rear brake system
- Service battery - Test battery charge and clean terminals
- Check engine timing
- Inspect EGR system
- Inspect fuel tank cap and lines
- Road test vehicle
- Wash and vacuum (Saturday only coupon offer**)
- Bravada rear axle service, drain and flush rear axle and refill fluid (Add $99.95 (price in New York))
- Timing belt replacement (Catera only - additional parts not included) (Add $289.95 (price in New York))

Additional Maintenance
- Replace fuel filter $49.95
- Service battery terminals, check alternator output, lead test battery $39.95
- Electronic balance, 4 wheels (includes tire rotation) $69.95
- Align front suspension $89.95
- Align front and rear suspension (computerized state of the art system) $99.95
- Air conditioning service (leak test and add one pound of refrigerant)(extra refrigerant at additional charge) $129.95
- Drain and refill antifreeze $89.95
- Flush and clean fuel injectors $99.95
- Service automatic transmission/transaxle (replace necessary fluid and pan gasket, clean filter screen)(additional charge for Northstar) $99.95
- Replace front brake pads (resurfacing of rotors not included) $169.95 / additional charge to resurface rotors $75.00 / Extra charge for trucks and 4 wheel drive vehicles and other various types of vehicles; see your advisor
- Replace rear brake shoes (resurfacing of rotors not included) $169.95 / additional charge to resurface rotors $75.00 / Extra charge for trucks and 4 wheel drive vehicles and other various types of vehicles; see your advisor
- Emissions service - includes air filter, PCV filter and fuel filter $99.95
- Vehicle check for road trip (includes chassis lube, oil and filter change, plus 21 point safety check, tires and wheels, brake system, light system and signals, steering, shocks, front and rear suspension, fuel and exhaust systems, road test vehicle $88.95
- Complete alarm system, Lo Jack and remote starters (see your service advisor)

Prices do not include sales tax or disposal fee, wheel weights or liquid additives. Prices are subject to change without notice. These prices cannot be combined with any other advertised specials.

* Some pricing, services and offers may be different or unavailable in your area
**Offer may not be available in your area

Northstar Maintenance / Tune up (check this discussion for references): (back to the top)

These are the steps I followed to change the plugs and wires.

• 1 Remove the engine cover (after opening the hood)

• 2 Remove the strut brace. This is easy and gives you a lot of room to work

• 3 Remove the coil pack. Two bolts on the back and two bolts on the side (10mm). This will give you easy access to all four rear spark plugs.

• 4 Remove the spark plug wire and change the spark plug. Do one plug at a time. You should not have any problem removing the plugs in the back. Use a spark plug socket - the one with rubber to hold the spark plug in place and an extension.

• 5 Change the spark plug wires one at a time making sure you put it back on the correct terminal. This is pretty foolproof. The number of the cylinder is labeled on the block and the terminal is labeled on the coilpack AND in some case it is labeled on the wire as well.

• 6 Put everything back in place.

The fuel filter is on the driver's side of the car underneath the (rear) door.

• 1 Remove the fuel pump fuse and run the car until it stalls. This will remove most of the pressure from the fuel line.

• 2 Jack the car.

• 3 Locate the fuel filter and remove it. I used a screwdriver to break the plastic piece that holds it there - I'm pretty sure there's a better way to do it.

• 4 Put the new filter in place using the new plastic retainer.

• 5 Don't forget to put the fuel pump fuse back!

More tips:

Clean the throttle body bore to eliminate and sticky throttle feel and/or idle speed control issues. Just hold the throttle open and spray the bore with carb cleaner and scrub with an old toothbrush. Disconnect the battery negative cable for 30 secs to reset the idle speed learn offsets for the clean throttle body.

Service the coolant system... This is the single most important thing to insure long life of the engine. The green silicated coolant needs to be replaced every 2-3 years / 24-32 K miles to maintain an adequate concentration of corrosion inhibitors in the coolant. Replace the coolant with fresh 50/50 coolant/distilled water and add the coolant supplement to the radiator hose as described.

Northstar Oil Consumption (check this discussion for references): (back to the top)

It is not unusual for a Northstar to use more oil than some other engines. It is a high performance engine and has to allow a little more oil to the top rings for lube as as well as down the 32 valve guides.

Design intent for oil consumption would put the engine at about 4000 miles per quart consumption but due to the variables in production parameters there are engines that will use 1 quart per 1000-1500 miles.... perfectly normal and acceptable... but more oil consumption than "intended". Nothing will be wrong with the engine but the continuous oil adds are aggravating. If this is the case then understand that the engine is probably going to run a long long time like that as the cylinder walls , rings, valve guides, etc. like all that oil that you are putting in and the continuous oil adds fortify the used oil in the sump and replenish the additive package in the oil that is slowly depleted under normal usage.

Comparing the 4.9 to the Northstar is an apples to oranges deal. The 4.9 is an excellent engine for it's purpose but does not offer nearly the performance, durability, fuel economy and emission control capability of the Northstar. The Northstar is a high output engine and likes to be "used".

The best way to minimize oil consumption in a Northstar is to keep the sump filled slightly low (many are continuously overfilled) by only checking the oil level when hot and only filling the sump with 7 quarts of oil (7.5 with a dry filter at a change.) A typical 8 quart fill at a change is "required" to put the oil level on the full mark when cold but is actually overfilling the crankcase promoting oil consumption.

Use conventional mineral oil (synthetic is not required at all) as it tends to provide better oil consumption.

An last, but not least, air the engine out frequently. It likes to be used and red-line upshifts at WOT help promote clean combustion chambers, exercise the piston rings to keep them free of carbon buildup and keep them mobile and to ensure the engine is broken in and maximum sealing is obtained. The Northstar does not like to be babied around. It likes to be run hard frequently with a WOT blast in merging or whatever.... Even engines reported to use 1 quart per 1500 miles tend to improve to 2500 miles per quart or better when subjected to a regular schedule of use and "abuse"...


The subject of oil consumption really does not have a "final" answer. The fact is that there is some variability in oil consumption in all production engines.... regardless of who makes them on which continent. All the manufacturers recognize this and virtually all of them will call oil consumption as great as 1 quart in 1000 miles "normal" "acceptable" "allowable" "within production tolerances" etc... This doesn't mean that all engines will get 1000 MPQ or that the engine was designed to get 1000 just recognizes the fact that there are going to be some engines that get 1000 MPQ that will be perfectly fine upon disassembly and will have nothing "wrong" with them.

The variables that usually enter into oil consumption are primarily associated with the piston/ring/cylinder bore. The number of valves or type of valve actuation has little to do with it.

The single biggest variable and the one that has been discussed at great length on this forum is the cylinder bore finish or the cylinder honing pattern. The higher performance the engine is the more attention must be paid to the honing pattern and retention of oil on the cylinder walls to lubricate the piston and rings at full load , high RPM operation. The Northstar engine uses a very aggressive cylinder bore finish that tends to retain a lot of oil to protect the piston and rings. When the blocks are honed at the factory there is a tolerance in the bore finish due to the fact that the honing stones will wear and need replacement. A brand new stone gives a slightly more aggressive pattern than a "used" a block honed with new stones will have a more aggressive finish and most likely will use more oil.

Another variable is bore roundness. Like it or not, the bores tend to "move" slightly as the engine heats up and cools down and bolt tensions relax, etc. over time. All this contributes to slight bore out of roundness that is not bad or good...just different.

Carbon buildup in the rings and ring sealing are also variables that come into play with break in, operating schedule, type of oil used, etc.

The one thing that I can attest to is that many, many customer oil consumption complaint engines have been torn down with absolutely nothing wrong found. The engines are often reassembled and put into test cars and driven by the engineers and more often than not the high oil consumption does not repeat itself !!! The single biggest common cause seems to be breakin...or lack there of. Many, many oil consuming NOrthstar engines are "fixed" by some full throttle operation. I often joke about "driving it like you stole it" but it really is no joke. The Northstar engine was designed as a high performance engine to be run hard and fast. Those that are run hard typically exhibit excellent ring seal, little carbon build up and good oil economy. We have seen engines with tens of thousands of miles on them that the rings have not sealed or mated to the sides of the ring grooves because the operating schedule was so light duty. The moral here is to flog it .... often.

In any case, the nice thing about the engines with the more aggressive honing pattern is that the pistons, rings and bores will last forever. It is very common to tear down a 200,000 mile Northstar engine and still see the original honing pattern in the cylinders. There is never any sign of cylinder wall wear and the idea of a wear "ridge" at the top of the cylinder bore is something that is laughable on a Northstar.

The other nice thing about a little oil consumption is that it adds tremendous safety factor to the oil change interval. Nothing could be better for the engine than an occasional quart of fresh oil. You can take the worst oil on the market and add a fresh quart every 1000 miles and over the life of the engine the wear will be better than an engine run on the best oil with no adds between changes.

While no one in the engineering community wants high oil consumption the fact is that there is some variability in the oil consumption of an engine manufactured at the rate of 1200 per day. The specs of what is "normal" simply reflects does not imply that all engines would get this or that something is wrong with and engine that gets more or less oil consumption.

There have been a lot of engineering changes over the years on the Northstar aimed at reducing the overall oil consumption and reducing the variability in the oil consumption of different engines. Many changes have been made to the honing process to make it more consistent. Changes to the piston and ring groove treatment have been made to make it more resistant to wear, pound out and micro welding at low oil retention rates. Regardless, there is still some variability.

One other thing that affects oil consumption, or the customers perception of oil consumption, is the move toward longer and longer change intervals. With the allowable change interval reaching as high as 12,500 miles on a 2003 Northstar if the oil life monitor is followed this could mean the addition of 3,4 or 5 quarts of oil to a very healthy engine. If the owner changes their oil every 2000 or 3000 miles, despite the oil life monitor recommendations, then they would not have to add any oil between changes. The oil consumption is the same....the amount added between changes is all that is different. Yet, many customers do not make the distinction. Field surveyors repeatedly show that "acceptable" oil consumption means "not having to add between changes"...whatever MPQ that is...???

The issue of oil consumption is very emotional , too, as many people perceive higher oil consumption as 'poor quality" or an indication that something is wrong. Blue smoke, fouling plugs, noise, a sign of something wrong. Using 1 quart in 1000 miles might be perfectly normal for an engine that has the high limit "rough" hone finish and is perfectly in spec...yet it will be perceived differently.

The Northstar engine in particular was designed to be a high performance engine and to perform well at high speeds and high loads. The engines are tested at loads and speeds for time periods few customers will ever be able to duplicate. It is unfortunate that the engineering that goes into making the engine capable of such running sometimes contributes to more oil consumption... especially as the production machining tolerances are taken into account.

The items mentioned about overfilling also apply. Make sure that the system is not overfilled as any excess oil will be pushed out the PCV. The best bet is to always check the oil hot and keep it midway between the add and full mark. Don't always top off and don't top off cold to the full mark as that will overfill the sump.

Hope this helps rather than adding more fuel to the fire... so to speak.

Incidentally, there is a lot in the message board / forum archives... check using "oil consumption" and read up. Always keep in mind that for every "oil burner" you read about on the internet there are 10,000 or more driving around perfectly fine that the people are not posting about... You are always going to read about the horror cases on the internet.

Transmission Flushing - Good or bad? (check this discussion for references): (back to the top)

Never, ever flush a transmission. There is no "safe" way to flush a transmission unless you own the flush machine and control it yourself.

Flushing a transmission has several pitfalls...

The most obvious is that the last vehicle hooked up to that flushing machine probably was on it's last leg and was generating tons of debris. Most owners, when the transmission starts to act up, rush to get a "flush" in the fervent hope that it will cure the problem. So... flush machines, by definition, see the worst of the worst. If the lines aren't cleaned, hooked up improperly, oil is reused or recycled, etc....then you are screwed as your transmission gets the dose of debris from the last transmission . No matter how good the intentions of the shop, one simple mistake and your transmission gets the debris.

Flushing is supposed to negate the need for removing the pan, cleaning the debris and replacing the filter... BS. There is considerable debris coating the inside of the transmission pan with miles as anyone who has done this can attest. That is part of the maintenance, removing the pan, cleaning the screens and replacing the filter and cleaning the pan.

All that debris in the pan is laying around in areas where there is little oil flow by definition... it tends to settle in the areas where the oil is quiet and just lies there not hurting anything.... until the "flush" stirs it up and circulates it thru the transmission. What a concept...

Reverse flush????? What logic makes anyone think that it is a good idea to reverse the oil flow path in a reverse flush and flush sediment and debris into areas that are normally protected by filters, etc...???? Stupid idea. Period. No other way to describe it.

"Transmission flush" machines are money makers for the shops and dealerships because they are quick and easy and they can actually charge more money for it under the guise of it being "better" for the transmission... when it is really a detriment.... suckers are born every day...

Read the factory service manuals and point out the place where a transmission "flush" is recommended.

So what if all the oil cannot be removed. A "flush" doesn't remove it all either.

If you really really want to replace as much oil as possible in the transmission, drain the pan, service it by removing/cleaning/changing the filter and reassemble. Refill the transmission with fresh fluid. Disconnect one of the cooler lines at the radiator, put it into a bucket and start the engine. Let the transmission oil pump purge the old oil into the bucket so that nothing is subjected to abnormal oil flow. Start pouring oil into the transmission to keep it full while the idling engine/transmission oil pump purges the fluid thru the system. Easy and quick and gets ALL the fluid out... and eliminates any risk of hooking up to a "flush machine".

I know this is about 4.1/4.5/4.9 engines but be aware that on the Northstar engines/4T80E transmissions there is a hidden drain plug for the transmission side cover that requires that the bottom pan be removed to drain the side cover oil storage area. The idea of flushing a 4T80E is even more ludicrous than a 4T60 transmission for this reason.

The 4T60 and 4T80 transmissions are similar in that both store oil in the side cover...but they do it differently. The 4T60 transmission with the 4.x engines stores oil in the side cover only when HOT. There is a bimetal thermostatic valve that closes causing side cover oil to be trapped behind a weir or dam. So, change the oil in a 4T60 transmission when it is cold to get the most oil out... The 4T80 transmission is a dry sump unit that ALWAYS stores it's oil in the side cover. There is a scavenge pump that scavenges the oil from the bottom pan to the side cover all the time. That is why there is a hidden drain plug underneath the bottom pan to drain the side cover when the pan is off for service.

FORGET THE IDEA OF FLUSHING YOUR TRANSMISSIONS. Normal transmission maintenance is a good idea. Drop the bottom pan, change the filter and clean everything up and refill the transmission with fresh fluid. Do the cooler line/bucket purge if you are really fastidious about changing all the fluid... but... DO NOT hook your transmission up to a flush machine.

Really now, would you get a blood transfusion from an unknown source that is reusing needles... about the same thing if you think about it. A flush will do absolutely nothing more than a good drain and refill will accomplish... and potentially a lot of harm. Do not take the risk. Just because some have had good experiences (or the lack of a bad experience) with a flush does NOT mean that they will always go good.

Camel Mode - Loss of Coolant Protection (check this discussion for references): (back to the top)

The Northstar engine has a loss of coolant protection mode where four cylinders are shut down (the injectors are turned off) so they can cool themselves by pumping only air... Once that set of four cylinders is cooler, they're turned back on and then the other four cylinders are shut down to cool. The two groups of cylinders continue to shut down alternately so as to protect the engine during a severe overheating situation and allow the driver to reach a safe place rather than be stranded on the side of the road.

It has been nick named "camel mode" since the engine can run without water in it.

Camel mode is VERY effective on the Northstar for several reasons...

1. It is an all aluminum engine. Without coolant it transfers heat very effectively through the entire engine...and to the oil. The oil starts to become a secondary heat sink and cooling medium along with the air pumping thru the cylinders with no combustion going on.

2. The engine has a lot of power and it is in relatively lighter weight passenger cars. has ample power on only four cylinders to still move the car.

Don't forget that the four "dead" cylinders are still pumping air (and making no power) so the pumping losses are huge. Much of the power of the running four cylinders is being eaten up to pump air thru the other four. So it isn't as though you have only a four cylinder engine to run the car on. More like you have an equivalent 2.5 cylinders worth of power to run the car.

3. The system was heavily developed on the Northstar originally so it is specifically tailored to that engine.

The camel mode or loss of coolant protection is very very effective on a Northstar as many folks can attest. It is way way more than just marketing ploy. I have personally left work several times with a development car with no coolant in it and driven 45 miles home in limp home mode and then drove back in the next day. And the engine survived MANY trips like this with me and other people and was fine when filled with coolant. Max speed is about 45-50 MPH and it will slow considerably on any grade but it will get you to safety.

Several magazines have tested the system with excellent results. Motor Trend, years ago, took a car to Gilla Bend, drained the coolant and drove back to LA. Car was on a press junket at Sears Point raceway several months later and it shocked the MT scribes to see it there running fine after they had done the loss of coolant test with it....and returned it without telling anyone in the Cadillac press fleet operation.

In addition, USAC took several cars and did the independent, third party testing of the system to validate the advertising copy and such for the networks and magazines.

Other GM vehicles have a version of the limp home mode also, but it is never marketed as a 50 miles at 50 MPH type of system or that it has that capability. The basic function is there but it cannot work as well as the system in the Northstar in all applications:

1. The trucks are heavy and the power in four cylinder mode is not enough to move the vehicle very fast and very far.

2. Some of the engines are not all aluminum and the iron blocks do not transfer heat as well and the engine develops hot spots that minimize the effectiveness of the system.

The limp home is there but it is marginally effective. It is better than nothing...and any cooling system failure has the ability to just stop the car immediately so it may help and may not in any given case.

Other cars (like some of the four cylinder, all aluminum engines) have little or no success with the limp home mode due to the low power available when in only two cylinders...with less than one cylinder of power available due to the pumping losses.

The trans fluid in the modern cars is easily good for the life of the car in normal driving. Running it to 100K is very "safe" and will cause no harm to the trans.

Transmission Fluid Information (check this discussion for references): (back to the top)

Transmission fluid is not like engine oil. It is not exposed to blow by and by products of combustion. It does not see copius amounts of water from blowby on coldstarts. There is not much to deplete the lubricating characteristics of the trans oil and the antiwear and special friction modifier packages are very robust and stable. The temperature of the transmission fluid is pretty carefully controlled in the cooling development for the car. About the only thing that will shorten the transmission fluid's life is excessive heat and excessive heat for long periods of time. Since the modern transmission fluid has a high synthetic content it is pretty stable even at temps approaching 300°F. So...the things that govern and oil change in an engine do NOT apply to the transmission. Not at all.

The transmission fluid life "counter" in the display uses the transmission temperature as a means of judging the transmission fluid life. As long as nothing is done that the algorithm sees to shorten the life of the fluid it will stay at 100% virtually forever. If you start towing trailers or running extended heavy load operation you will see the transmission fluid life decrement fairly rapidly. If it is "stuck" on 100% then that means that the operating parameters that the PCM sees for the transmission fluid have all remained well within the guidelines for life time use of the transmission fluid. The transmission oil life monitor does not operate the same way the engine oil life monitor operates so you will typically see it stay at 100% in most cases.

Changing Coolant and Using the Correct Number of Tablets (check this discussion for references) (more) (more) (more) (more) : (back to the top)

The manual will show three of the GM coolant supplement pellets for the Northstar. The 4.x engines were recommended for six of them due to the greater chance of an internal leak of coolant directly into the oil. I always recommend six of the GM coolant supplement pellets / two tubes of the BarsLeaks golden seal powder for either engine. It just provides extra protection against leakage and will not hurt a thing.

A good time to drain and refill the system with fresh 50/50 DexCool/distilled water is when the 5-year/100K life of the DexCool from the OEM fill is near....

The water pump will be the easiest one you have ever changed...hard to believe the dealers can somehow justify charging $570 to change one - which is about $450 profit, I would say... With the special tool it's a snap. Remember that the water pump cartridge is removed by turning it clockwise as viewed from over the left front fender looking into the water pump cavity from the backside after removing the cover. It is installed by turning the special tool counterclockwise...a "left handed thread" install. When the old pump is out remember the o-ring seal that is in a groove in the water crossover casting. Look inside the housing when the water pump is out and you will see it. Put a new o-ring in the groove (should be in the kit with the pump) and make sure it is seated and lubed with antifreeze when installing the new pump.

Check the water pump drive belt and tensioner. The tensioner may need to be exercised and the pivot lubed to keep it moving freely.

Warming-Up Your Cadillac's Northstar Properly (check this discussion for references): (back to the top)

The best thing for the car and engine is to start it up and drive it. Period. Idling for warmup is completely unnecessary and just wastes fuel and time. The engine is designed to be operated immediately. It takes about 2 seconds for oil to circulate thru the engine even in the worst case coldest day so that is just not an issue. About the only case for waiting to "warm it up" is for the heater to work or the windshield defroster to come up to temp. And even then, the heat and defrost will warm up faster driving it.

I am not condoning hopping in on a cold day and starting the engine and flooring it to 100... just drive away normally and sanely and the engine and trans will function fine and warm up the best. Idling is absolutely not required. The Northstar engine is actually cold-protected against too high of an RPM as the heavy throttle upshifts will be forced sooner and there is a lower rev limiter on the engine until it warms up sufficiently so you really can't hurt it even if you try... The only thing to worry about here is the oil pressure cold on high RPM operation. That is why the rev limiter is lowered cold... so the oil pump cannot overpressurize the system with cold oil.

Several Ways to Check for a Blown Head Gasket (check this discussion for references): (back to the top)

- Start the engine cold with the pressure cap off the pressurized surge tank. Watch the coolant in the surge tank for signs of bubbling or "false boilling". If so then it may be a sign that combustion pressure is entering the system through a failed head gasket.

- Pump up the cooling sytem pressure with a cooling system pressure tester pump. Hold it at 15 PSI for several hours. Keep pumping it up if the pressure drops. In the meantime, pull the plugs. After several hours holding pressure, rotate the engine with the starter with the plugs out. Watch for coolant spewing out from the spark plug ports as a sign of a leaking head gasket.

- With the cooling system full, apply 120 PSI shop air to each of the combustion chambers, one at a time, through the spark plug port. Make an adapter out of an old spark plug shell and run shop air to the port. Rotate the engine so that the valves for that cylinder are closed. Watch the coolant in the surge tank for bubbling. If the chamber holds the 120 PSI with no bubbling then chances are the head gasket is fine.

How Often Should I Change My Oil? The GM Oil Life System: (back to the top)

Q: How does the GM Oil Life System (OLS) work?
A: Vehicle maintenance intervals of three months or 3,000 miles no longer apply to vehicles equipped with this system.Instead of an actual oil-condition sensor, the GM Oil Life System relies on a computer-based software algorithm that continuously monitors engine-operating conditions and driver use to determine when an oil change is necessary.GM has calibrated the system for a variety of vehicles based on millions of test miles over a period of years.The system is now installed on more than 20 million GM vehicles.

Q: How do I operate the system?
A: The GM Oil Life System is very easy to use.Refer to your Owner’s Manual for a description of your specific vehicle’s change oil light or message and instructions for resetting the system.When the algorithm determines that your vehicle needs maintenance,the change oil light or message will illuminate on the instrument panel or the driver information center at start-up.You should have your vehicle’s oil changed within 600 miles of the odometer reading at the time the change oil light or message first illuminates. Immediately after the oil change, reset the system according to instructions in your Owner’s Manual. After the reset,the change oil light or message will no longer illuminate at engine start-up until the oil needs to be changed again.

Q: How many miles can I expect to go between oil changes when using this system?
A: It will vary.The beauty of the GM Oil Life System is that it automatically adjusts the oil-change interval based upon engine characteristics, your driving habits, and the climate in which you have been operating your vehicle. For instance, mild highway driving in a warm climate will maximize the interval between required oil changes. Depending on the vehicle,this could be as high as 12,000 miles.On the other hand, short-trip driving in a cold climate may limit the interval between oil changes to 3,000 miles or less. In general, most people who combine city and highway driving find that the GM Oil Life System will indicate the vehicle needs an oil change every 5,000 to 6,000 miles.Most people maintain consistent driving habits.This means their mileage between required oil changes will be consistent.

Q: What happens if I change the oil and forget to reset the system?
A: Since the GM Oil Life System does not actually sense oil condition, it is important that the engine computer knows when your vehicle has had an oil change.It registers this information through the reset operation described inyour Owner’s Manual.The change oil light or message will illuminate at start-up until the system is reset.The more miles you drive without resetting the system,the more inaccurate the GM Oil Life System will be.If you drive more than 500 miles after an oil change without resetting the GM Oil Life System,you should default your oil-change interval back to 3,000 miles.After you change the oil and reset the system, you may resume normal use of the system.

Q: I change my oil every 3,000 miles.How does this system help me?
A: You may continue to change your oil every 3,000 miles if you choose, but the GM Oil Life System allows you to extend your mileage between changes without harming your engine. It takes the guesswork out of your vehicle maintenance needs,calculates when you need maintenance, and it provides efficiency and convenience.It also is an economically sound practice that protects the environment by minimizing the amount of oil used and discarded. Remember, however, to reset the system after the oil change or you will get a false reading from your change oil light or message.

Q: Do I have to use special oil?
A: The GM Oil Life System calibrates your needs based on the use of standard factory-fill automotive engine oil that displays the “Starburst”API® Certification Mark. This verifies that the American Petroleum Institute certifies it for use in gasoline engines.Make sure to read your Owner’s Manual to select oil with the viscosity and grade that is correct for your engine. Any oil you use should carry the API “Starburst”mark. The Corvette and a few other GM vehicles (2004 CTS/STS/SRX) are the only ones that require synthetic oil.

Q: The oil-change service station recommends that I change the oil every 3,000 miles. Why should I not believe them?
A: The 3,000-mile oil change is a very conservative approach to maintaining your vehicle that dates back to 1968. Since then, there has been many advances in both engine design and oil technology. These advancements, in conjunction with the GM Oil Life System, allow you to increase engine oil-change intervals without risking harm to the engine.

Q: I change my own oil. Should I reset the system myself?A: You may reset the system according to the instructions in your Owner’s Manual, or you may ask your selling dealer for assistance.

Q: Will I damage the vehicle if I don't change the oil soon after the change oil light or message comes on?
A: As your Owner’s Manual specifies, you should change the oil as soon as possible after you see this indicator.We recommend that you change it no more than 600 miles after the message first appears.

Q: Do I have to check my oil level now that my vehicle is equipped with the GM Oil Life System?
A: Yes, because the system does not sense oil level.As your Owner’s Manual specifies, we recommend that you check your oil every time you stop for gasoline.

Q: Will I void my warranty if I don't follow the GM Oil Life System regimen?
A: To maintain your warranty, you must comply with your Owner’s Manual recommendations. We suggest you read it.

Q: I had my vehicle’s oil changed recently but my GM Oil Life System indicator is still on.Why?
A: If the light is still on,the system may not have been reset when you changed your oil.You may reset it within 500 miles of your last oil change. If your vehicle has exceeded this mileage, change the oil at 3,000 miles and then reset the system.

Q: I still prefer to have my oil changed at about 3,500 miles.What should I do?
A: It is OK to change your oil before your vehicle notifies you that you are due for an oil change. Be sure, however, to reset the system when you change the oil, even if the GM Oil Life System light/message has not illuminated.

Q: I have driven 6,000 miles since my last oil change.My change oil light/message has not come on, but my oil seems dirty. Do I have a problem?
A: Your vehicle’s oil may discolor under normal conditions, depending on driving conditions. Refer to your Owner’s Manual for additional information.

Q:Can any dealer other than my selling dealer perform Simplified Maintenance?
A: We recommend that you care for your vehicle through your selling dealer so you can build a relationship with the team that sold you your vehicle. However, any GM Goodwrench dealer can perform Simplified Maintenance and reset the GM Oil Life System for you.

Q: During the summer,I drive my vehicle in a very hot climate. Do I need to change the oil more often?
A: The GM Oil Life System calculates your vehicle’s needs based on a wide range of driving conditions, including more stressful situations such as severe climates, trailer towing, or stop-and-go operation.There is no need for you to override the recommendation of the GM Oil Life System.

Q: I continue to get 3,000-mile follow-up mailers from my GM dealer. What should I do?
A: Inform your servicing dealer that you prefer to follow the Simplified Maintenance schedule determined by the GM Oil Life System and would like them to adjust the type of follow-up mailings they send you.

Q: I have a 2002 model GM vehicle with the GM Oil Life System.Can I use the Simplified Maintenance schedule with it?
A: Because Simplified Maintenance was not yet introduced before the 2004 Model Year, continue to use the recommendations in your Owner’s Manual for that vehicle.

Occasional Full-Throttle Acceleration Is Good For Your Engine (check this discussion for references): (back to the top)

There are many advantages to occasional full throttle accelerations with a Northstar and any engine.

It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston - they actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant - also harder to break-in and seat the rings to the sides of the ring-lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related, to some extent, with the rings never seating to the sides of the ring-grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring-grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particles, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. They're designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing; no carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the transmission shifting out of the question if you are worried about hurting it. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy over-run conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy over-run which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow-out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed/developed/validated to be run hard. It was expected that people would use the performance of the engine - which few people seem to do. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low-tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I have had, once the owner started doing the WOTs and using the power of the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" at WOT then you are not doing enough WOTs...) etc... A bit of judicious use of the other end of the throttle travel is a GOOD thing...

How can I improve the performance of a Northstar exhaust system? (check this discussion for references): (back to the top)

In all honesty the real cork will ultimately be the production exhaust manifolds and the "cross through" pipe that goes from the front bank to the rear bank to route the front bank exhaust rearward. The production parts are packaging-constrained and designed for emissions performance to light the catalytic converter quickly. That being said, they are not THAT bad... But the real hotrod Northstars like CHRFAB is putting into sand rails and such run headers.

I would go with 2.5 to 3 inch pipe from the cat rearward. It will have to be a custom bent setup as I don't know of any avialable sources for the prebent parts. Several people have tried different brand mufflers for low backpressure. Flowmaster, Corsa, etc... You'll have to do some searching in the archives for their reports on sound quality and noise. They will definitely be louder but probably tolerable.

There's really no practical way to put real exhaust headers on the transverse mounted Northstar engines due to space, packaging and routing constraints. The idea of a "free flow" exhaust sytem is not lost on the engineers that designed the production car... but... packaging, lack of space, the cross-thru pipe design, emissions performance, durability of the exhaust manifolds and system, etc... All got in the way of real headers...

One thing that will help free up a few horse power is to get the exhaust manifolds off and have them extrude-honed. There are a lot of sharp edges and corners in the fabricated manifolds that can be ground, smoothed and radiused. Not a huge gain here and a lot of work to pull the manifolds and such but if you want the most power, the manifold rework with the low backpressure system will provide the most. I would say that the ultimate exhaust on a transverse passenger car with extrude-honed manifolds, large pipes and Flowmaster style muffler would probably provide 20-25 HP at peak power.

How do I Disable Daytime Running Lights (DRLs)? (check this discussion for references): (back to the top)

Press the Dome Override button 4 times within 6 seconds and wait for the chime.
Note: This also turns off the Automatic Headlights.

How do I Reset the Oil Life Indicator? (check this discussion for references): (back to the top)

With the key in the on position, motor off, press the accelerator to the floor 3 times and watch the Driver Info Center. It should flash, in orange, 'Oil Life Reset'.

© 2007 (information)

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