The Stovebolt Site Forums The Shop Area Engine Shop Good thermostats?

Tired of less-than-worthless thermostats. Anyone know what a consistently good one is? Looking at getting a few Stant 45358 and/or 13358's. Surely to God those should work?

Backstory to my newly-found hatred:

My truck was running hotter than it should, so I replaced the thermostat. Boiled the old one, and sure enough, lazily opened at 190 or so, didn't open all the way until about 210. Marked 180, Motorcraft. Brass.

So, all good, I thought. New thermostat was a MotoRad 180, Mr Gasket package, made in Canada. Looked like it should work. New water pump, too.

But, no. Runs 190 or so, and on first warm-up it climbs straight to 210 or so before opening and coming back to 180-190.

My father's truck has been doing this for a couple years now, always figured it had to be the t-stat, but he had swapped it out several times. All the thermostats have holes in them to let air out. My truck did not do this prior to changing the t-stat. Tired of this BS!

Look on ebay for a NOS or NORS that is 25 years old, I have used Stant Superstats with good luck but the last one I got didn't work very good.

66Submarine mine is doing the same thing ,, so is it the stat ?? it opens at 180 does that mean it runs at the temp ?? mine does the same thing open at 170 the climbs to 190 to 200 at red lights ,, i am thinking it might be the rad not the stat ??

just saying
thanks

lilrobo: if it's only at lights while idling and not going down the road, it's probably the fan. When you're going 50MPH the airflow through the radiator is sufficient to cool it with no fan at all 99% of the time. When you sit at a light, though, your fan isn't pulling enough air to keep it cool. You might notice if you bring the engine up to say, 1,500RPM, the temp drops due to the fan pulling more air. Try to get the fan up close to the rad and run a shroud, you shouldn't have any trouble then.

My problem is temp spike on initial warm-up. (And running hot at speed, to some degree.)

So the Stant stuff is also hit and miss now, Don? That blows. I guess I'll get a few and test before I put them in, I'll keep an eye out for old ones, too.

if your cooking it on the stove are you using an accuarate thermometer

Thermometer seemed good, and the temp gauge agrees. I just drove the truck again, same thing. Spikes to 210 degrees or better and quickly drops back to 180-190 when it finally opens.

If I put a 180 in my 216 there is an initial overshoot to around 200 and then it settles to 180. I thought that was due to the catching up with the heat load created by the closed thermostat. With my 160 installed there is still an overshoot but not as dramatic.

Somewhere I read that someone offers a high flow thermostat. I can't remember who makes them.

Maybe it needs a burp?
Have you had the heater open and passing thru when refilling the H2O? I've known a trapped air pocket to cause this sort of grief before... in kids and engines.

I know that the Stant superstats have a small check valve to help fill cooling system and not end up with air pockets.

Can you still get 165 degree thermostats?? John

Yes, but most parts books do not list them for the 216/235/261 anymore. Not sure why, since they were what the factory put in them. Oddly enough, they are listed for the V8s, which will directly interchange with the 6.

All the thermostats have holes in them to let air pockets out. I could understand/deal with even a 10 degree overshoot, but my fathers truck has spiked to more than 240 degrees before! Then, of course, it quickly cools to 180, say maybe five to ten seconds. Seems like a great way to ruin good heads to me. My other truck has a good thermostat in it, climbs up to 180 and stays within five degrees or so. A 180 degree thermostat allowing temps to spike to 210+ degrees for absolutely no reason is unacceptable, IMO.

You may want to look again, although some have a way to purge air very few do.
My 1997 Blazer did not and it would spike like you said until I drilled a hole in the flange.

A short lived spike should not really hurt you. If its just a quick one I truly doubt the engine is getting that hot. Raise the hood and see if it smells hot, or even lay your hand on it....very carefully. And, as an after thought try a infra-red thermostat and see what it says the engine is doing, as well as check the top tank when thermostat opens up and see what you get.
Take the cap off and put your thermometer down in the neck and see what the water reads when the thermostat opens.... are you sure the radiator doesn't need rodding out? Maybe a good flush job?? Just throwing out idea's....

I threw away the shut off valve that's mounted on the thermostat housing and added a by-pass valve to the defroster(don't have a heater). Now I get no overshoot in normal operation and in three times of draining and refilling got no air pockets, no burping, no overshoot.

This one had a hole in it as purchased, my father is pretty sure he drilled holes in all the ones he put in his truck (I also came across one he took out and it had a hole in it). Not enough to flow a meaningful amount of water, mind you, but plenty to let air out, which is the idea.

Alvin, the spike itself is slow building, temp just keeps climbing past 180 because it's not flowing any water. It's when it opens that it cools abruptly. Which is what I'm worried about, a 210-240 degree head getting hit with cool water every single time you drive it. My fathers truck also has vortec heads, which have a reputation for cracking. His truck will also seem to climb rapidly in temp somewhat, I presume because the heads don't have the bypass in them, and are getting locally hot, showing as an additional spike on the gauge when it starts flowing water.

No top/overflow tank, radiator is a brand new aluminum one. Wouldn't be the radiator anyway, only happens at warm-up.

The heater is hooked up on this truck, and it climbs in temp slowly, so I don't think that's it. Didn't do it with the old t-stat, either.

The water temp sensor and the thermostat are at opposite ends of the head... so while the front end is allowing water to the radiator the rear end is still warming up.

You should see an even greater 'spike' right after shutdown as all that hot water sits in the block.

If anything the radiator cap should vent if the water gets high enough to boil... I don't think you are going to melt anything at 220F

put the old thermostat back in. You said it didn't do that with the old thermostat. If it works don't fix it.

The temp sender is actually right under the thermostat. The temp increase after shutdown is due to heat soak from the hotter exhaust manifolds/heads/block, etc.

The radiator doesn't vent or boil, because in my case, all the heat is in the engine. This is right after starting from cold. Instead of warming up to 180, it overshoots to 210-220, then quickly drops back as the thermostat opens. The radiator is still cold while it's happening.

Anyway, I got my new thermostats in. Boiling them didn't instill great hope, so I drilled a hole big enough to flow water (1/8-3/16, can't remember) in one and put it in. I'll see if that works. Didn't seem to do it on the drive back, but the temp was still at 140 when I left, so it wasn't cold.

The old thermostat didn't work that great itself, although it didn't do this.

OH, it was a thought anyway. I have resigned myself to getting ripped off with nearly anything I buy any more. Even Levis aren't made in america any more.