I just got an 02 coupe a few weeks ago and earlier this week, the temp jumped to the red zone and cooled back down to the 200 range all within about a minute. In my non-expertise opinion, I'm thinking it was the thermostat sticking. Anyway, it happened again before I could get it to service, but this time it didn't cool back down. I was out of town and luckily only a block from a dealer. Now they're saying there is combustion mixing with the coolant. Again, I'm no mechanic but I'm thinking now it has either a craked head or block right? Still under factory warranty thank god since a new engine is probably in the $9-10K range.
Anyone have any thoughts on the cause? I was thinking the thermostat stuck for good this time and the engine overheated to the point it cracked the head or block. Aren't there any failsafes that would prevent so much damage all from a $50 part. In retrospect, maybe it wouldn't have done that much damage if I would have just turned the car off as soon as it got hot, but the last time it cooled down almost immediately. I'm just crossing my finger I just wind up with a whole new engine. I was only about 4K miles from the factory warranty expiring (now I know for sure I need to extend it).

 

Sounds like it was low on coolant or had an air pocket in the system. they can be a pain to purge sometimes when air gets trapped in it. My experience with a gauge that fluctuates rapidly (quick to hit the red zone & quick to return to normal) is not enough coolant in the system. Not sure if this was caused by your cracked head/block or if driving it this way on a road trip with low coolant caused the problem. I have heard this can happen when aluminum is exposed to high temps, then the coolant hits the empty passages and cools them quickly by 100 degrees or so. I am no mechanic, just a guess. Glad you are under warranty. Scott

 

Tough to say. If they are saying there are combustion products in the coolant, maybe the high coolant temp was just a symptom, not a cause.
I've not yet heard of a theromstat failing, but I'm sure it could happen.

As an FYI, the PCM does have an overtemp protection mode when coolant temp reaches something like 265 (sorry, don't have my service manual with me so can't check exact temp).

Last year I had a serpentine belt come off, and at a later race, a coolant hose come off. In both cases, the coolant over heated. Motor survived both cases, but died later in the year due to a seized bearing (prior to my switch to AMSOIL). Not sure if the previous losses of coolant and the ultimate failure were related or not.

Good luck with your repair.

 

Could be as simple as a BAD HEAD GASKET. Aluminum heads warp easy when they get HOT.
Either way if it is under warrenty they should be able to take care of the problem.

BC

 

Turns out not a cracked head or block. Chevy service guy said the bolts on the head were a little loose when they removed the heads. Head was pressure tested and came out fine. Said that due to loose bolts, the head got warped and they machined it straight and are re-assembling now.
I was concerned that the structural integrity of the metal would be joepardized if it warped so I called another Chevy service dept. They said that machining was an approriate action since the head probably didn't warp from heat but rather a loose bolt and that the work would be warrantied for 12/12K.
Can't help but be sceptical but since they are not going to give me a new engine, at least that problem is documented and covered for another year. All the more reason to make sure I extend the warranty since the factory warranty expires in another 4K miles.

 

I suppose the "silver lining in every cloud" for you must be the fact that your motor has slightly more compression than before!

 

Yeah the guy told me that it would have just a bit higher compression that when it left the factory. Oh well. Extending the warranty to 100K anyway so if it breaks again...their problem.

 

Sorry to hear you experienced this kind of problem.

I would have thought they'd install a thicker head gasket to compensate for the machining and maintain the same compression ratio. Not a problem if both heads were machined but not desirable if only one side of the engine was changed. You'll be getting more power from the higher compression on one bank of cylinders creating an 'unbalanced' engine from a power standpoint, which could result in faster engine wear. This is why professional engine builders are careful to "cc" their heads, i.e., match the volumes of each combustion chamber to ensure that compression ratios and power are as similar in each cylinder as possible. just my .02......glad you're getting an extended warranty.

 

They are machining both heads which is good.

 

 

The saga continues. Service now says after getting everything back together, it's still overheating. The heads that didn't have a crack but were warped have been machined. I'm assuming that when you replace the heads, you would be able to tell if the head gasket is bad. So what else could cause compustion to mix with the coolant? Cracked block is all I can think of. I don't understand how they wouldn't have been able to tell prior to all of this though. Well, maybe there's still a shot at that new engine afterall. We'll see what they say they will troubleshoot next...

 

What a nightmare. Good luck!

 

Sounds like they didn't find out what was causing the overheating in the first place. I'd think they'd pressure test the cooling system after reassembly to make sure there was no other damage to the engine (other than the heads). That would have shown if there was leakage elsewhere, i.e. cracked block.

I would think that the heads were warped from overheating, not overheating caused by warped heads. Subsequently, the techs should have gone through the cooling system components to ensure everything was functioning properly prior to start-up on the reassembled engine.

Good luck and keep us informed.

 

I agree with all that. I have been skeptical of this dealers abilities since I dropped my car off there. unfortunately, I didn't have a choice as I was traveling about 5 hours from home and it was the only place there. I just keep reassuring myself that some junior technician is at least on a hotline with someone from GM who really knows what to do. What a mess...

 

Finally got it back. Turns out it was the damn radiator that was all clogged. I guess that because it was clogged and it overheated, that is what caused the heads to warp, not a "loose bolt" like they said. Anyway, got the rad flushed and they machined both heads and put new gaskets on so everything runs fine now. I just wonder what made them look at the heads in the first place unless they saw steam or something. I would think if you bring a car in for overheating, that rad would be one of the first things to check. Oh well, got it back so I'm happy.

 

BMADSEN

I find it very difficult to believe that the radiator was clogged! (I'm not doubting your word but the word of the dealer) I have a 98 MN6 Coupe with 62,000 miles on it and I just changed the coolant. After I drained it out, I thought that I should have just poured it back in. That's how clean it was!
The new DEXCOOL was just a bit brighter in color.

The several ways that I know of that someone can destroy their cooling system are:

Add the GREEN antifreeze to the DEXCOOL
Too little antifreeze (FREEZE UP)
Too much antifreeze (Reduces the cooling effect of the coolant)
Run the engine without a thermostat. (engine runs too cold)
Stuck shut stat.
Run the eng low on coolant
Break the belt and run the engine

What is the past history of your car? Do you have any idea if any one off these things happened to your car?

BC

 

I wish I new more about the history. I only bought it 1 month ago from a Toyota dealership. I had about 27K miles on it. I did the carfax report to make sure there were no problems. But as far as all of the other potential items you mentioned below, unfortunately I have no idea. Stuck thermostat was my first guess when this all started because it was very speratic for a week.

I had this work done WAAAAY down in south Texas (Clark Chevrolet in McAllen) because that is where I was for business and that's where my car overheated. The service consultant literally told me his tech had to keep calling the Chevy tech hotline because his guys didn't know what to do. I need to schedule my car to get a recall on the steering column (some kind of recall). I thought about asking them to check it out again because when I've called them before, they have 3 guys that always works on vettes.

 

Thats a GREAT idea. Maybe they can spot anything the ***** at the other dealership may have goofed up! Sorry to see that you are having this sort of issue. For what it is worth, I have a 98 coupe MN6 and an 02 ZO6 and have very little mechanical issues with either car. Just electrical issues with the 98 which I resolved myself!

Good luck

Bill Curlee

 

I heard that there's a class action lawsuit ot investigation, or something, going on with GM because of the DexCool. Something out the coolant gelling up and clogging things. I bet that's what happened to you. I was told that people are replacing it with Zerex Orange.

 

Wow that's interesting. I had no idea but sure enough do a search on google and all kind of reports some up:

http://www.cwcd.com/CM/MassTorts/MassTorts5.asp

http://www.bigclassaction.com/class_action/dexcool.html

http://www.imcool.com/articles/antif...le-Excerpt.pdf

www.dexcoolcase.com

www.consumeraffairs.com/automotive/
gm_dexcool.html

Now I'm not sure whether it is best to keep the Dexcool in there and just make sure it is always full or replace with something like Amsoil???