The Stovebolt Site Forums The Shop Area General Truck Talk Thermostat,no thermostat, that is the question

Someone told me that some trucks will run cooler with a thermostat than without one at all. Mine is a 235 3/4 ton. Something about a thermostat causing the water to stay in the radiator longer so it runs cooler. Is there anything to this?? I have always thought that removing it would allow for more circulation thus cooler temps. Am I way off base on this? Anybody have any experience with this? thanks!! slowgoer

You need a thermostat. Engines run best at a certain temperature, and the thermostat keeps the engine at that temperature. So when you start out cold, the coolant does not circulate to any great degree, which lets the engine warm faster. And yes, without a thermostat, the engine can run too hot, because the coolant is circulating too fast.

agree,,,,,,,,,,,,,,,,,sort of like eating apple pie,, just works better with a little ice creme on top.

Apple pie with ice cream!!!!!Now I'm hungry again!!
Yes you do need a thermostat.With a weak cooling system I have cut the center out of an old thermostat to make a restrictor.This will keep the water in the radiator longer for better cooling.

I guess that does make sense, I am going to install the thermostat but I read in another post about system being airlocked. How do you check for that and what if it is, how is it fixed??thanks again!!

While were on this, what is the recommended temperature for the thermostat? This is a 3/4 ton Chevy with 235,it came with a 216, so should I get something like a 165 degree or 180 or what? This radiator is thicker and heavier than the half ton trucks I have dealt with. I don't know if they tend to run at higher temps or not. It's good that you guys know this stuff!

Slow,

The "temperature" of a thermostat is the temp at which the 'stat opens. It controls how fast the engine warms up.

My understanding is that you want the engine to run in the 180-220 range for best efficiency. The 165 or 180 thermostat might be too cold unless you have an old cooling system or are running a lot of engine -- at 180 degrees the system would be working at full power to reduce engine temps. Of course, if you're running in slow traffic or very hot weather, this might compensate.

What I usually do is put one in and run it for a while to see how I like it -- they're easy to change.

Brian

I try to change mine out twice a year. 165 for summer driving and a 180 for winter. Doesn't always happen but the heater sure works a lot better in the winter with the 180.

Brian; thanks for the info. Let me see if I have this straight. If I want the engine to run at, like you said is best, say around 200, then a 165 degree will not be as efficient as a 180? Let me ask it differently? A 165 degree will not keep it at 165 as will a 180 not keep engine at 180? So a 200 degree will keep the engine cooler and be more efficient than than the 180? I am not completely crazy, though it may sound like it here.

I didn't see your response Bruce before I posted but what about the airlocked system? Can somebody inform me about the symptoms,cause and fix??

To keep your system from being air locked, simply drill a small hole in the flange part of your thermostat to let the air escape from the block when filling your cooling system.

Small hole. I drilled a 1/8" hole in the thermostat in a 97 GMC. It dramatically increased the warm-up time. If it was easier to get to, I'd replace the thermostat with one that has a much smaller hole. Use the smallest bit you can find at the local hardware store.

The thermostat opens at the specified temperature. If you install a 165° stat, the water temp will reach 165° before the water starts to circulate. Installing a 200° stat will keep your engine temp at least 200°.

Thanks for the info. I will install one today, amd see how it goes.

Slow,

The 200 won't keep it COOLER, but it will keep it more efficient. Try it, and see if you find the truck running too hot. If you do, swap down to the 180.

There are so many factors -- the health of the cooling system, the size of the engine, the richness/leanness of the carb, the temperature, the engine RPMs, etc, that it's hard to sit here and work out a perfect answer. Try it and see

Brian

Instead of drilling a hole in the thermostat flange, just open it by hand and wedge a plain old aspirin in the gap. It will allow the air to escape during coolant filling preventing airlocks. By the time the engine is warmed up the aspirin will be dissolved and the thermostat will function normally. Learned this from an old timer a long time ago. John

I went to a local parts store and got the thermostat and while there I asked about the airhole to prevent airlock. He knew about it and held it up to the light and you could a very small hole probably less than 1/16" which was not visible unless it was held to the light. This guy is a friend of mine who bought this store probably less than a year ago. One of his suppliers gave him a call about 6 months ago and asked if he remembered being entered in a contest that was going on were you were automatically entered for just purchasing his normal store stock. He said he thought he vaguely remembered. The guy went on to inform him that he had just one the grand prize, a brand new Mustand GT. He said he would not believe it till he saw but it was delivered a couple of months later. It would just make me mad if someone said I just won a Ford but I guess its better than a set of wiper blades.

That's a good one, John - I'll remember that. The other reason for the hole(s) though, is to act as a primitive bypass if the thermostat freezes shut. In that case, I guess the owner takes the aspirin.

on our demo derby cars, we cut the inner part of the stat out, leaving just the opening that is as if the stat is full open. that way it cant freze closed and cause overheating. its better to have a good thermostat, but in a pinch, having a cut open one in your tool box will get ya out of trouble.

you need the tremostate for every day street use. a 235 engine is not ment to run at 200. a 165 may be too cold. thermostat keeps the engine at a uniform temperature. i would try a 170 if they still make them. higher temp means higher pressure on the cooling system. use a new cap. most engines have a cast in termostae by pass chanel of some sort. all modern thermostates have an air relise 'hole' about 1/16 or less.