OK, drove the car a little hard last weekend and lost another thermostat. Anyone have any recommendations for a better quality brand of thermostat? Stock one and one from Autozone both failed.

 

I've always had good luck with the ones from NAPA in my other cars.

 

The occurrance of repeated thermostat failures is due to something OTHER THAN thermostat failure. Sounds like faulty installation to me.

But, as suggested, Napa has pretty good parts.

 

I have had an issue where I replaced a failed thermostat with a thermostat that failed right away. Drove me nuts trying to find out what was wrong since it couldn't possibly be the thermostat since it was brand new!!

I'd try another thermostat and see if the problem returns. If it does you know it's not the thermostats at that point and then you have to get serious about finding the problem.

 

I have had brand new ones fail. They were installed properly and just failed.

Like many things are just not made as good as they used to be.

 

For those that are not familiar with the thermostats on our cars (at least the 2.4) there is a rubber seal on the actual valve where as most older thermostats just had metal to metal seal between the valve and the body of the stat. The failure point on the new stats is this rubber seal. It breaks loose from the valve and wedges between the valve and the seat causing the valve to stay partly open.

I really think it is a design flaw that causes the issue. For one thing a number of people on this board have had the same failure.

I have been working on cars for 35 plus years and am a trained mechanic, so I believe I can install the stat properly. Having said that anyone with ideas as to what else can be the cause of these failures, pinched hose, clogged passages, whatever I would be interested in your ideas.

 

Guess no one else has any ideas either..............

 

You nailed it. And it's not just HHRs or for that matter GM vehicles doing it.

 

if all the different type thermostats have the same problem of the seal failure, then i would delete the seal and put just enough gasket sealer from a tube to hold it in..the trick would be to use just enough that you wouldn't have any extra sealer breaking off causing anouther or the same problem...it only has to hold what 12-20 lbs of pressure? if it had a tiny leak i don't think it would effect anything...don't that thermostat have a tiny hole in it anyway ? i know that some do.

 

OK lets see if I can clear this issue up a little.
The thermostat has two rubber seals. There is the typical rubber seal around the outside of the thermostat that seals the housing. it gets clamped between the housings and the outside edge of the stat. This seal keeps the it from leaking outside of the system. Pretty much been the standard for a long time.

The issue come in from the second rubber seal this seal is actually on the moving part or the valve of the thermostat. On older stats this valve made a metal to metal contact with the seat on the body of the stat. One these new stats there is no meltal to metal contact between the valve and the seat. It appears at some point it was decided that the stat needed to seal more completely, so a rubber seal was added to to the actual valve.

The issue is that part of the rubber breaks free from the valve and wedges between the valve and the seat holding the valve partially open. When this happens it takes longer to heat up the coolant. This causes the computer to set a coolant temp failure.

If the rubber seal is removed from the valve the disc will actually close fully giving metal to metal contact. I had thought to try doing just this but there are issues with this. The first is, will it seat well enough to bring the temp up fast enough for the computer. Second when you remove the rubber it leaves a series of small holes in the disc as the rubber is held in place not by adhesive but by being formed so it passes through these small holes. Will these holes allow to much leakage again causing the engine to warm too slowly.

I may try to fill the holes with either solder or epoxy and see if the engine will warm up fast enough without the rubber seal on the valve. If not my next try will be to add adhesive to the rubber seal on the valve and see if that helps hold the seal in place better.

If anyone is really interested I will post pictures of the actual stat and seals in question.