Frequent T-Stat failure

[Hank]

My 91 goes through 2 t-stats a year.

NOTE: No engine or gasket problem exists. Read on:

No water in oil, oil in water, no coolant or oil loss, no bubbling, no exhaust gases in radiator. Used smog sniffer.

When the T-stat works it runs perfectly cool. Radiator, hoses, waterpump are all new/newer.

I have tried, Stant, Jet, AutoZone, Discount, OEM brands. Prices ranges from 2.00 to 15.00 and all the same, they just crap out in about 6 months.

I have tried straight water, 50/50, straight coolant, no change.

Jiggle pin is up. No air in system.

When I pull the failed t-stats and put them in boiling water they physically do not open.

Any suggestions on a T-stat that works?

 

[mabulok]

Last one I put in was from autozn and I don't even remember the brand. But it hasn't failed in over a year. The one previous was the original and it worked for 3 years before the plunger broke off. Maybe try installing a new pressure cap. And make sure you're running 50/50, using either filtered water, softener treated water, or DI water to avoid the possiblity of minerals in your system from hard water.

 

[jgilbs]

try flushing out your cooling system. maybe there are contaniments floating around that could lead to failure. I know when I replaced my water pump, my tstat failed because a small piece of liquid gasket started to circulate in the system and got stuck on the tstat.

 

[JGAMBLE]

I agree with mabulok, try a new radiator cap. At this point it seems the most logical step.

 

[Hank]

Thanks guys but... forgot to mention.

Radiator: new
Cap: new (2 new caps)
Coolant: new mixture tried everything.
Water pump: new
Hoses: new

It is ALL new...


It runs cool, no overheating, NOTHING until the t-stat physically fails... When I pull the t-stats and there is no gunk, nothing....

Major flushing done in past which solved a ping/hot problem. Was some blockage. Flushed the hell out of it till no more chunks came out.

No material/junk in the cooling system at all.


Either I have purchased a bunch of crappy t-stats in a row or the t-stat gods just don't like me.


I'm just baffled...

 

[Billy177]

you may just be unluckey to you take frequent short trips

 

[Glacier991]

I had several failures on mine as well, but suddenly they stopped. Some company was making T'stats that would only fail in the OPEN position, or would go there is they did, or something, and I was ready to try theirs next. So far I haven't had to.

 

[B1942]

Welcome to the club

Hank,
I nave been chasing this problem for years, "65 289, "76 302, "86 2.9, "96 4.0. Like you I've tried every brand out there and still replace Tstats at least twice a year. I've learned to live with it.
B1942

My 91 goes through 2 t-stats a year.

NOTE: No engine or gasket problem exists. Read on:

No water in oil, oil in water, no coolant or oil loss, no bubbling, no exhaust gases in radiator. Used smog sniffer.

When the T-stat works it runs perfectly cool. Radiator, hoses, waterpump are all new/newer.

I have tried, Stant, Jet, AutoZone, Discount, OEM brands. Prices ranges from 2.00 to 15.00 and all the same, they just crap out in about 6 months.

I have tried straight water, 50/50, straight coolant, no change.

Jiggle pin is up. No air in system.

When I pull the failed t-stats and put them in boiling water they physically do not open.

Any suggestions on a T-stat that works?

 

[Hank]

Ok, at least I'm not the only one going nuts here..

New t-stat in for a week and so far working fine. Probably should go get another spare and put it in the glove box for when this one takes a dive..

 

[bigred93explrer]

Got a question for you. Since you are an expert at replacing the thermostat in a first gen, what is the easiest way to get the bottom bolt off of the thermostat housing. I replaced my thermostat yesterday(2nd one in a month) and I always have the hardest time getting at that bolt.

 

[Hank]

There seems to be no easy way other than dropping the tensioner assembly. I found the next best way is to drop the belt, letting the tensioner swing all the way left. Then I get to the third bolt with a 1/4" drive, extension and a wobbly socket.

For assembly I put a little RTV on the threads and use my fingers as pliers to thread the bolt in a bit..

 

[bigred93explrer]

ok that sounds reasonable. I had the hardest time with that little bolt. The other two werent really an issue but the bottom was really hard to get to and even worse to put back in because i kept dropping it. Thanks for the advice