my northstar is overheating WHY

[gabyllac]

i live in arizona 110 degreez my car overheating when i was driving at wot so i change my themalstat sry for the spelling lol and drove it fine 3 weeks later my raidator leakin change that week later weather went up to 112 degrees and my car overheated it when up to 249 degrees but the first time it overheated it was 260degrees wat is wrong with my northstar plz help

[Cadillac Jim]

The Northstar (and most other modern engines) will overheat if the antifreeze content in the coolant is less than 50%, particularly in hot weather and/or at highway speeds. If someone has added water lately, that will cause it.

The easy thing is to add anti-freeze so that you are running 60% to 70% instead of 50%. You can get an inexpesive coolant anti-freeze level checker at any auto parts store. If in doubt, or if it's low in anti-freeze content, drain the coolant and add two gallons of anti-freeze (be sure and use DexCool, marked on the bottle for late-model GM products) and top it off with water.

If that doesn't do it, you should have it looked at by a radiator shop. They should do a pressure check to make sure that you don't have a leak somewhere, that the new radiator is OK, and that you don't have head gasket leakage.

[KHE]

Do not run Dexcool at concentrations higher than 50/50. 50/50 will give adequate performance under most climate conditions. The first thing I would do is verify that the coolant concentration is 50/50 (freeze point of -34F). If you use one of the cheap Prestone testers, verify it's accuracy by testing a known 50/50 concentration of coolant.

If that checks out, disconnect the 3/8" line from the surge tank anv verify that coolant pees out when the engine is idling. If not, there is an obstruction in the line or the hollow bolt on the waterpump housing. If that checks OK, the waterpump impeller may have separated from the shaft - that would be a rare thing though.

If all the above checks OK, then pressure test each cylinder with 120psi shop air when each cylinder is at top dead center and all four valves for the respective cylinder are closed - there is a TON of information in the archives on that procedure.

[PAUL T]

Always use a 50/50 mixture of coolant and distilled water to the top. Check the waterpump belt to see if the idler is not binding or loose. Check all hoses and their connections. Check for a cracked surge tank. Is it losing coolant? On the ground or out the exhaust?

[BodybyFisher]

Personally I would take it easy on your car when the heat is above 95 degrees. I would not recommend WOT's in that kind of heat, but that is me. You are located in the hottest place in the country, I don't envy you.

Did you use an OEM AC DELCO thermostat? If not change it immediately to an AC DELCO. Did you use the cooling supplement tablets when the stat and radiator were replaced? If not give it a full dose now. Check your water pump belt for wear and make sure the tensioner is not binding. Check your cap to make sure it holds its rated pressure.

With your heat I would not be surprised that you would run in the 240 degree range in traffic. The 260 concerns me. Follow the advice given above (except for running a higher than 50/50 concentration with Dexcool). Pressure test the cooling system. When you do work on your cooling system it requires a couple of warm up/cooling cycles for it to stabilize.

Let us know how this works out, Mike

[Cadillac Jim]

I would add this to BodybyFisher's comments -- make sure that you have the GM radiator cap that is sold for your vehicle. The importance of this cannot be underestimated, particularly for an overheating Northstar.

[gabyllac]

okay thank for the info i work during the week its hard for me to check it but on the weekend im going to check it okay. it overheated monday coming out the highway temp was 250 so it peuk some coolant out i added water then i went to a autozone and put coolant and my system it runnin the green stuff tell me why dont noe shouldent it run the orange stuff? and the thermastat i boght it at checkers ,and you guy mention a hose i should disconnect while idleing no clue sry and my idler pully makein noies like ticking sound when i reve it and u guys mention a additive witch one and were to get it sry for all the questions just tryin to fix my wondafull caddy . question what the diffence for a checkers thermalstat than a gm stat. and i drove it to work today and drove it allmost like a old lady lol 45mile to work one way in 110degree weather and the coolant temp whent up to 230 and drop to 222 degrees good or bad thing. again thank for all the respons hope we can get to the point in my caddy

[BodybyFisher]

okay thank for the info i work during the week its hard for me to check it but on the weekend im going to check it okay. it overheated monday coming out the highway temp was 250 so it peuk some coolant out i added water then i went to a autozone and put coolant and my system it runnin the green stuff tell me why dont noe shouldent it run the orange stuff? and the thermastat i boght it at checkers ,and you guy mention a hose i should disconnect while idleing no clue sry and my idler pully makein noies like ticking sound when i reve it and u guys mention a additive witch one and were to get it sry for all the questions just tryin to fix my wondafull caddy . question what the diffence for a checkers thermalstat than a gm stat. and i drove it to work today and drove it allmost like a old lady lol 45mile to work one way in 110degree weather and the coolant temp whent up to 230 and drop to 222 degrees good or bad thing. again thank for all the respons hope we can get to the point in my caddy

You said:

"it overheated monday coming out the highway temp was 250 so it peuk some coolant out i added water then i went to a autozone and put coolant and my system"

My question is, did it PUKE coolant out at 250 degrees? If it did, it means that 1) you are boiling at too low a temp meaning that you have less than a 50/50 mix or 2) your system is NOT holding pressure. Check your coolant concentration and pressure test your cooling system.

ALSO: NEVER NEVER put WATER in your system. Water will boil at a lower temp and you mess up the coolant concentration. Also while we are on the subject of water use DISTILLED water when you make the 50/50 mix to eliminate the minerals, chlorine and impurities in tap water. Living in Arizona (my favorite place by the way) you SHOULD keep pre-mixed coolant in your car at all times (but I wear a belt and suspenders )

You said:

"it runnin the green stuff tell me why dont noe shouldent it run the orange stuff"

YES, your car SHOULD be running with DEXCOOL (orange). If someone put GREEN coolant in and you are NOW using GREEN, you will need to change the coolant every 2 years or 24,000 miles now as the corrosion protection of GREEN is not as good as the orange.

You said:

"the thermastat i boght it at checkers ,and you guy mention a hose i should disconnect while idleing no clue sry and my idler pully makein noies like ticking sound when i reve it and u guys mention a additive witch one and were to get it sry for all the questions just tryin to fix my wondafull caddy . question what the diffence for a checkers thermalstat than a gm stat"

The OEM GM stat was designed and calibrated for your engine, with it, there are NO guessing games. With the Checkers stat? who knows. The OEM GM stat has a long tail on it that reaches deep into the engine to read temps. When you are having overheating problems you need to ELIMINATE potential problems.

Your idler pulley probably needs replacing if it is ticking. Take your serp belt off and spin the idler wheel to see if the bearing is noisy and/or dry sounding or loose.

The hose you are looking for runs across the engine at the front and connects to the tank, disconnect it and see if coolant is flowing. If this hose is clogged, the cooling system will not be able to purge itself of air.

The cooling supplement can be gotten at the Cadillac dealer, or see this link, Bars Leak also sells the same stuff see the picture SCOTTY posted of the supplement here:

http://caddyinfo.ipbhost.com/index.php?sho...ling+supplement

The tablets are to be crushed and put into the upper radiator hose NOT the tank. Make sure the engine is cool. Use all six if it has not been used before. Once you put the tablets in, tighten the hose and run the engine to normal operating temp.

You said:

"i drove it to work today and drove it allmost like a old lady lol 45mile to work one way in 110degree weather and the coolant temp whent up to 230 and drop to 222 degrees good or bad thing"

In 110 degrees, those coolant temps are very good. Last week I was in Virginia Beach and I was running similar coolant temps in 98 degree heat.

[Cadillac Jim]

There's a big red flag here. If you have a 1999 DeVille, it should NOT have the green anti-freeze. I would go to a radiator shop ASAP and have the system power-flushed and the coolant replaced with DexCool. While it's there you can have them diagnose the problem. It may be nothing more than the wrong anti-freeze.

There's no reason that your car should overheat in Arizona at 110 F so long as you are moving at 30 mph or faster. If it overheats, something needs fixing.

Your coolant mix must be between 50% and 70% anti-freeze. The 1997 factory manual, page 6-185, "Filling Procedure," includes these instructions:

NOTICE: When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50,000 km (30,000 mi) or 24 months.

NOTICE: Pure coolant can be added to raise the boiling point of the coolant, but too much will affect the freezing point. Do not use a solution stronger than 70 percent, as the freeze level rises rapidly after this point. Pure coolant will freeze at -22 C (-8 F).

If you are looking at an anti-freeze checker, 50% corresponds to protction to -37 C (-34 F).

[BodybyFisher]

There's a big red flag here. If you have a 1999 DeVille, it should NOT have the green anti-freeze. I would go to a radiator shop ASAP and have the system power-flushed and the coolant replaced with DexCool. While it's there you can have them diagnose the problem. It may be nothing more than the wrong anti-freeze.

There's no reason that your car should overheat in Arizona at 110 F so long as you are moving at 30 mph or faster. If it overheats, something needs fixing.

Nope.....

Once the cooling system has been contaminated with GREEN, the GREEN plates the system with silicates and it can not be flushed out.

If you have GREEN keep using it, there will be NO benefit to using DEXCOOL at that point. The only drawback to using GREEN now if the flush cycle is NOW 2 years or 24,000 miles instead of 5 years or 100,000 miles for the ORANGE. The GREEN will provide the same cooling and anti-freeze protection, but not the extended corrosion protection of Dexcool.

[KHE]

There's a big red flag here. If you have a 1999 DeVille, it should NOT have the green anti-freeze. I would go to a radiator shop ASAP and have the system power-flushed and the coolant replaced with DexCool. While it's there you can have them diagnose the problem. It may be nothing more than the wrong anti-freeze.

There's no reason that your car should overheat in Arizona at 110 F so long as you are moving at 30 mph or faster. If it overheats, something needs fixing.

Once green coolant has been introduced into the system, the silicates plate the internals of the cooling system. It is good to switch back to DexCool but the DexCool will need to be changed every two years as the silicates deplete the corrosion inhibitors in the Dexcool. There is no way to rid the system of the silicates once they have been introduced.

[adallak]

The Northstar (and most other modern engines) will overheat if the antifreeze content in the coolant is less than 50%, particularly in hot weather and/or at highway speeds. If someone has added water lately, that will cause it.

The easy thing is to add anti-freeze so that you are running 60% to 70% instead of 50%. You can get an inexpesive coolant anti-freeze level checker at any auto parts store. If in doubt, or if it's low in anti-freeze content, drain the coolant and add two gallons of anti-freeze (be sure and use DexCool, marked on the bottle for late-model GM products) and top it off with water.

If that doesn't do it, you should have it looked at by a radiator shop. They should do a pressure check to make sure that you don't have a leak somewhere, that the new radiator is OK, and that you don't have head gasket leakage.

The water is actually more effective coolant than ethylene glycol. Increasing the concentration of the latter will not cool the engine down but only will increase the boiling point.

[Cadillac Jim]

The Northstar (and most other modern engines) will overheat if the antifreeze content in the coolant is less than 50%, particularly in hot weather and/or at highway speeds. If someone has added water lately, that will cause it.

The easy thing is to add anti-freeze so that you are running 60% to 70% instead of 50%. You can get an inexpensive coolant anti-freeze level checker at any auto parts store. If in doubt, or if it's low in anti-freeze content, drain the coolant and add two gallons of anti-freeze (be sure and use DexCool, marked on the bottle for late-model GM products) and top it off with water.

If that doesn't do it, you should have it looked at by a radiator shop. They should do a pressure check to make sure that you don't have a leak somewhere, that the new radiator is OK, and that you don't have head gasket leakage.

The water is actually more effective coolant than ethylene glycol. Increasing the concentration of the latter will not cool the engine down but only will increase the boiling point.

adallak -- agreed, nothing is better than water as a coolant because it absorbs more calories per gram than anything else except exotics like liquid sodium or such. The problem with too little antifreeze in a Northstar -- or most other modern engines -- is that hot spots in the head will cause steam bubbles to form when the engine is under load if the coolant boiling point isn't high enough. That's no big deal, but the thermostat normally opens and closes often and bubbles accumulate under a closed thermostat before they are absorbed, isolating the thermostat for a minute or two while the bubbles go through the bypass, and the temperature will spike, generating a bunch more steam bubbles, etc. Sliding around town may not cause it, but a Northstar on the highway at 65 mph will overheat as it crests every hill if it doesn't have enough antifreeze, regardless of the outside temperature.

I'm looking at the 1997 shop manual, in Diagnostic Information and Procedures, Engine Overheating, page 6-178. The first four items read:

1. Check for a loss of system pressure [pressure check first!].
2. Inspect and repair any faulty hose connections.
3. Check for low coolant protection (-27 C/-34 F) [50% or better antifreeze!].
4. Test solution. Replace the coolant if necessary.

Please forgive repeating a paragraph from a previous post, but I think this bears repeating here, with the checklist items: The 1997 factory manual, page 6-185, "Filling Procedure," includes these instructions:

NOTICE: When adding coolant, use DEX-COOL® coolant. If silicated [old-style green] coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50,000 km (30,000 mi) or 24 months.

NOTICE: Pure coolant can be added to raise the boiling point of the coolant, but too much will affect the freezing point. Do not use a solution stronger than 70 percent, as the freeze level rises rapidly after this point. Pure coolant will freeze at -22 C (-8 F).

[BodybyFisher]

NOTICE: When adding coolant, use DEX-COOL® coolant. If silicated [old-style green] coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50,000 km (30,000 mi) or 24 months.

Yes KHE stated that, but using GREEN is not what is causing the over heating problem in this Arizona car. That is what I was getting at.

[Cadillac Jim]

One thing that bothers me is that KHE said that once green was put into the system, the silicate sealer coats everything and cannot be flushed. And, KHE added that it depletes the antioxidants of the red anti-freeze so that it needed to be flushed every year or two just like the green. The shop manual says something that can be interpreted that way. I wonder if there is a way to power-flush the system with a solution that will remove the silicate sufficiently to restore the cooling system.

[KHE]

One thing that bothers me is that KHE said that once green was put into the system, the silicate sealer coats everything and cannot be flushed. And, KHE added that it depletes the antioxidants of the red anti-freeze so that it needed to be flushed every year or two just like the green. The shop manual says something that can be interpreted that way. I wonder if there is a way to power-flush the system with a solution that will remove the silicate sufficiently to restore the cooling system.

There is no practical/easy method to remove the silicates from the system once a DexCool system is contaminated with green coolant. Just switch back to DexCool and drain and refill with DexCool mixed 50/50 with distilled water every two years/24,000 miles. There is no need to flush the system unless it is plugged up. Flushing will only introduce tap water into the system which is typically high in mineral content. There are a lot of shops that seem to want to re-engineer the Northstar's cooling system by putting green coolant in there....they do not understand how abrasive silicates are to the water pump seal...

[epricedright]

My caddy is supposed to have green and I bought the Prestone that is supposed to be for both geen and dexcool cars. Is that stuff ok to use?

[KHE]

If it is the regular, green/yellow Prestone, it is fine.

[Ranger]

Jim,

I see you have been around here since '04. Perhaps you recall (as I do) out old Guru saying that the only difference between green & Dex is the longer life of Dex. Other than that I recall him saying that one is as good as the other for what it is intended. I was surprised to see the FSM say "NOTICE: When adding coolant, use DEX-COOL® coolant. If silicated [old-style green] coolant is added to the system, premature engine, heater core or radiator corrosion may result." I also recall him saying that once the system is plated, there is no way to "unplate" it so to speak. Just for the sake of mentioning it, before I new better I once put green coolant in my wifes '96 Bonneville just because I had it on hand. I flushed it out a day or two later on the advice of a dealer service rep. I had asked him how long it takes to plate the system and if I was already stuck with 2 yr. changes and he said I was OK. He never did say exactly how long it would take to plate the system, something I would still like to know.

[Cadillac Jim]

I would flush the coolant every two to three years regardless. I just had a bad experience because I let it go seven years. I had a documented case of head leakage, and overheating made the car unsitable for my use. At 117,000 miles with a lot of seepage on the o-ring and oil burning a continuing struggle involving two cans of CD-2 detergent additive about 1,000 miles after every oil change, I changed engines. I don't care what color it is, I'm flushing mine every three years, at least.

When in doubt, get radiator test strips that tell you whether you still have rust proteciton. Or, have a radiator shop that you trust check it for you.

Radiator test strips are in several catalogs but they are hard to find at parts shops. They don't sell much and they go out of date. I couldn't find them when I was trying to diagnose my overheating problem.