Fail Safe Thermo Stats

[Justin Fleming]

No really familiar with them, however there is one in my blazer. The truck can run for ever and the needle wont come up at all. The only way it builds heat is if I am driving down the road. Is it possible it failed safe and is leaking enough by to keep the truck from warming up and producing heat?

 

[ryoken]

never heard of such a thing.. sounds missing, or stuck open.. that's the only thing that will do that..

 

[blazer74]

I tried one in my ranger once. Took forever to get heat in the winter.

Took that sucker right back out, it's at the bottom of my pond.

 

[6872xtc]

I would bet that it is bypassing like you think. I have heard of them, but I like the the idea that I won't have to replace the thermostat if I get it too hot once.
I drilled too large of holes in a thermostat once, and it would move too much water past in the winter, combined with the heater, to get full engine temp.

 

[dhcomp]

Replace it with a brand name standard one. They fail out of the box more often than they actually fail in vehicles.

 

[warrpath4x4]

i have ran them before, the idea is when the thermostat fails it fails open so you don't overheat your engine. never had a problem with it not getting hot enough though

 

[dyeager535]

Unfortunately there isn't a brand out there that has been very reliable that I've heard of. Delco might be more likely to be good, but not guaranteed. Probably coming from China now too.

If it's running cold, only way that's possible is too much coolant bypassing the thermostat, or a bad temp gauge/sender. Thermostat is the more likely problem, pretty easy to tell, if the hoses aren't hot (and very pressurized) it's not warming up.

 

[Justin Fleming]

So this weekend I had time to swap out the thermo stat and sure as shit the fail safe had failed wide open

 

[diesel4me]

Better to lose your heat,and overcool the engine,rather than let it overheat and blow head gaskets or crack something...thats the whole idea behind a "fail safe" thermostat...but I know some "fail" as a matter of course,with no real "cause" too...

 

[dyeager535]

Better to lose your heat,and overcool the engine,rather than let it overheat and blow head gaskets or crack something...thats the whole idea behind a "fail safe" thermostat...but I know some "fail" as a matter of course,with no real "cause" too...

It would be nice if they'd just make garbage that worked like it was supposed to, as opposed to being designed to continue working WHEN it fails lol. I'm not old enough to have purchased any of these trucks or GM cars in the 80's new, but from what I've seen, the Delco thermostats were good for at LEAST 10 years in most cases.

 

[dhcomp]

Did exactly what it was designed to do. Replace with the most expensive brand name you can find, and move on.

 

[dyeager535]

Did exactly what it was designed to do. Replace with the most expensive brand name you can find, and move on.

Would be interesting to know who makes Stewart's stuff now, it used to be Robertshaw (which were good t-stats) but they are proud of these http://www.stewartcomponents.com/index.php?route=product/category&path=61

If they are good pieces, worth it.

 

[dhcomp]

To reiterate for the original poster, be sure to get the stock temp Tstat. Don't get a colder or hotter thinking it will help performance.

 

[Justin Fleming]

It did what it was supposed to do, however I almost think the first time it opened it failed open....I put a standard stat back in and all is good again...

 

[diesel4me]

Its been a crap shoot "forever" as far as getting a good thermostat right out of the box,ever since I've worked at parts stores in the 80's,they were one of the highest rate of failures out of all the parts we sold,next to electrical items..many failed right away,or never worked at all,and the engine would either overheat or run too cool..if you made it past the first few days,chances are it'd last years...

My dad also said he had many go bad too fast back in the 60's ,I still have about a half dozen new or "good used" ones still in boxes I found in a tool cabinet of his..all "name brands" like Roberstshaw and Stant,Gates,and a few OEM Mopar ones..he was a Mopar man,and those cars had the most cooling system woes out of all I think--the blocks used to rust bad,they would fill up with mud like pasty rust..

 

[Kain]

No really familiar with them, however there is one in my blazer. The truck can run for ever and the needle wont come up at all. The only way it builds heat is if I am driving down the road. Is it possible it failed safe and is leaking enough by to keep the truck from warming up and producing heat?

ya thats when it has failed , had one go in my blazer it did the same thing.I buy two keep one in the glove box just in case

 

[michael0584]

I always put the new ones i buy in a pot of water with a thermometer on the stove to see if they open up correctly before installing. I've found a few bad ones out of the box that way.

 

[Blue85]

I've never had a thermostat stick shut and as they wear they tend to stay open more and more, so what problem is there to solve? I would rather have one "not fail" than "fail safe". If you know it's stuck shut, you can take it out and run without one. If it's stuck open, you're cramming stuff in front of the radiator to try and get some heat in the winter.

I bet half of the thermostats that seem bad out of the box just have air in the system.

 

[ryoken]

as a marine mechanic, I worked for a marina for 5 yr's that EVERY winter they required all their raw-water cooled, gas motors to have a new therm installed... *coughmoneymakingscamcough*

so in other words, I've installed 100's of Merc therm's, probably a freakin thousand.... and NEVER had a bad one out of the package.. now Merc quality is pretty damn good usually, but still...

any bad ones people are getting, I would blame directly on the cheaparse manufacturer that is making them.. at least Merc has some quality control....

 

[diesel4me]

I've never had a thermostat stick shut and as they wear they tend to stay open more and more, so what problem is there to solve? I would rather have one "not fail" than "fail safe". If you know it's stuck shut, you can take it out and run without one. If it's stuck open, you're cramming stuff in front of the radiator to try and get some heat in the winter.

I bet half of the thermostats that seem bad out of the box just have air in the system.

OR,installed upside down!....

Many of the "defective" ones I took back at the store,I bet were probably OK,just put in wrong side facing down...when I'd ask the customer if they put it in spring side towards the block--I'd either get a blank stare,or a dirty look..

RTV gets in some too,use too much and it squishes out and gums up the works..

I suspect "marine" thermostats may have a more stringent quality control ,seeing there is no breakdown lane on the open ocean..they might actually test each one,instead of picking every 50th one off the assembly line for a random "test"..