nope...no water leaking into the car...i work with a bunch of mechanics and they are all completely baffled...i've come to the conclusion that my car is just stupid...maybe if it hapens a few more times gm will get tired of it and buy it back and give me a new one...

 

You say the thermostat is sticking. Is it sticking open or closed? If it sticks open, is it the rubber on the stat getting caught in it? If the rubber is deteriorating, have they flushed the cooling system and changed coolant?

If it is sticking closed and causing overheating, I assume they have put it in a pan of water to be sure it doesn't open.

How much coolant are you losing? I assume they cleaned the outside of the engine and added dye that shows up under blacklight to the coolant to check for leaks. If coolant is not leaking externally or into the oil, it would have to be going into a cylinder and out the tailpipe. If a large amount goes through, it could cause a problem with the oxygen sensor or catalytic converter. In small amounts it probably won't cause problems. Since combustion pressures are much higher, gases would likely go into the coolant also. There is a chemical test for that.

You could try a stop leak. Zecol Mendtite is the one I had the best results with. I've used it on diesel engines that have much higher compression ratios.

 

the dealer doesn't know what is causing the thermostat to fail...there is a slow leak of the coolant but they can't find it...i don't think they did a dye test...at least it's not showing they did on the repair order...they said the oil is clean and that there is no mixing...if (more like when) it happens again i'm going to tell the dealer to do a dye test because that's the only way to see if the coolant is gettiing into the combustion chamber and going out the exhaust...he wants to be able to do an overhaul on the enginge but he can't find anything wrong with the engine itself to warrant an overhaul...and gm won't cover an overhaul on the powertrain warranty for a bad thermostat...they might when it goes out again...but at this point it's a ticking time bomb as to when it will go out again...at least it's not the summer right now...it went out over the summer and that was not fun at all...

 

I guess you don't understand my question.

When the thermostat fails, does the engine get too hot? Overheating could be caused by the thermostat not opening. In that case, the thermostat would be removed, put in a pan of water with a thermometer. The water is slowly heated to the thermostat's rated opening temperature to see if it opens. If it opens, the thermostat is not causing the overheating. Many other things can cause overheating like a water pump, radiator with some internal blockage, external radiator blockage preventing air flow, cooling fan not operating properly or air in the system. Combustion gases getting into the coolant cause small bubbles decreasing the amount of heat the coolant can transfer from the engine to the radiator. In cooler weather it might not bother too much but in hot weather with the air conditioner operating it can cause overheating. When coolant pressure gets too high the radiator cap allows it to bleed off to the overflow tank. The air might be warm enough to carry some coolant vapor away to the atmosphere. Over time the coolant level will fall.

If the engine is running cold and doesn't reach operating temperature soon enough, error codes will be set causing the check engine light to come on. The thermostat could have something in it holding it open or it might open before it reaches the proper temperature. The same water test will show if it is opening before it reaches the rated temperature. If the system is full of coolant, the thermostat is about the only thing that can cause it to run too cold.

There must be some radiator shops in Arizona that can find the problem.

 

I'm not sure if when the thermostat fails if it is running hot...the gauge on the dash doesn't work and the coolant temp reading on the info screen just has dashes instead of the temp...my assumption is that it does get hot because somehow i'm losing coolant...the last time it went out when we popped the hood you could smell the heat coming off the engine...and after we put coolant in and drove it for 30 minutes you couldn't smell the heat anymore...i'm going to go to the store and get some coolant dye and drive it around for a week and check to see if it is going out the exhaust because i'm convinced & people i work with are convinced that that is where the coolant is going...cracked head or seal...if that doesn't show anything i'm taking it to my cousin's shop for them to check it out...

 

It sounds more like a low coolant problem than a thermostat problem. If the coolant level falls below the level of the temperature sender, the temperature will read below normal, thus the ---- on the DIC. Check your coolant daily by keeping the overflow bottle filled to the cold fill level as well as keeping the radiator filled to the top before starting the engine. Keep track of how much coolant you add.

 

Have them check the compression with the engine cold. I suspect that it is a leaking head gasket. The coolant is leaking into the cylinders which is vaporized when the engine is started. When the engine heats up it expands sealing the head gasket and stoping the leak. It might be stopped by retorquing the head. Just a thought.

 

the coolant level starts out fine...it's just slowly disappearing...i am now checking the level every weekend...but the thing is...i shouldn't have to be doing it that often...i should know by tonight if the coolant is going out the exhaust and if it is i'm going to take it to the dealer next week and leave it with them while i'm out of town...i have a case/claim open with chevy and they have now escalated it to the next level because i asked what they are going to do for me when it goes out again...i have zero confidence in my car right now...i'm afraid to take it out of town because i'm afraid it will go out again...the last thermostat lasted less than 3500 miles...which is less than half the amount from the previous thermostat...so at this rate it will go out in a month...the dealer claimed they did pressure testing when the engine was both hot and cold...i'm kinda hoping to see my exhaust pipe glow when i put a black light to it so that the dealer will be forced to take a closer look at the engine and fix it...

 

My bro's Nox had a similar problem... with only 59k on the clock... head gaskets were going out... had to replace them. $2k for the job. Dealership got GM to pick up 50% of the tab and the dealer compt'ed $250. But still.

 

leaky overflow reservoir? I believe they have a sniffer that can tell if there is coolant in the exhaust.