The Stovebolt Site Forums The Shop Area Engine Shop 235 running hot with Thermostat

Hey everyone..

I have a 1960 c10 with the stock 235 in it. When I first got it I noticed I didn't get any heat. Wala.. no thermostat!

So I put a 180 degree thermostat in. Got heat but the temp gage went all the way up just below the H for hot. The engine also wanted to stall when taking off in 1st.

Someone suggested testing the thermostat in hot water.. yup.. it works. then they suggested drilling a small 1/8th inch hole in the thermostat to let the air escape. Well.. it took longed to get to "H" but it did and again the engine wanted to stall.

So.. here is what I know.. the water is circulating so the pump should be working and the radiator seems clear. When it gets hot, the upper hose is somewhat hot, the lower hose seems cool but the heater hoses are too hot to touch.

Any ideas? Is 180 too much for the old girl? Do you think the radiator is clogged?

Any help is greatly appreciated!!

certainly not an expert but these are some things that might cause a heat up problem - heater coil could be dirty/plugged up and restricting the flow of water through the heater, you could have trapped air pockets in the system or as you mentioned your radiator might be dirty - also check to make sure your radiator cap is the proper one for your model of truck. they come in different "pounds of pressure" etc. I don't know about the 180 degree thermo.

Sounds like a clogged radiator, if the lower hose is cooler and the water pump is working.

Disconnect the upper and lower hose and let some tap water flow through the radiator from the top - it should flow out the bottom really fast.

Most original used rads that never or rarely got (reverse) flushed are more clogged than not.
Minerals in tap water create build up over time, despite anti-corrosion and anti-freeze.
Regular flushing helps, but radiators need to be recored every once in a while.

Make sure the thermostat is installed correctly.

I am running t180 in my trucks which is the specified thermo for the 235 so that should be no problem.

Hobert

a 180 should be fine, 165 will work too

I'd expect if the lower hose is cooler than the top, and the top one isn't super hot, the gauge is poor - they're not a real precision instrument

use the wife's candy/meat thermometer in the rad and see what the temp is there when the gauge says H

Bill

The fact that your heater hoses are hot indicate good flow through the heater core but the top hose should be hot whether the radiator was clogged or not. Sounds like the problem is in the thermostat area.

A 180 thermostat is good and I agree it sounds like a clogged rad. 235's are tricky to get all the air out but if you drilled a hole in the stat that should be ok. In a previous post a guy suggested wedging an aspirin in the stat and it dissolves after the air is purged.

Curt B.

I go along with the idea that either the thermostat is installed upside down or is not the right thermostat for the truck. It was running cool without a thermostat and it wouldn't have done that with a clogged radiator, nor would putting a thermostat in cause the radiator to clog. The top hose not being very hot tells me that water isn't flowing in sufficient quantity through the thermostat.

OK lets see....1st make sure the truck is running hot and just not the gauge..2nd if hot blow radiator check belt check lower hose for sucking together ,,back flush sys ,,check for blockage in radiator...doc

Take the thermostat out and see if it goes back to being too cool. If it does, it has to be the thermostat and no amount of other measures are going to do anything. The flat part of the thermostat goes up. The top radiator hose will not show the temperature of the engine coolant if the thermostat doesn't open; the heater hoses would be a better indicator when you are looking for a place for a temperature probe.

Put the thermostat in a pan of water on a cook stove and use a thermometer to see want temp it is opening at. Just because it's new does not mean it is even opening up.Make sure the pellit looking thing( usually brass or copper colored) is turned toward the motor when installed

An easy way to check for full circulation in the radiator is to run it up to operating temperature, shut the engine off and with the palm of your hand....feel around the whole radiator. A clogged radiator will have cool spots as well as real hot spots that are detectable by this simple check. You didn't mention if the truck cools off when you're moving or if it always stays hot, if it dumps water from the system.

I've found that once you get the cooling system clean and flowing free with a 50/50 mix of antifreeze and DISTILLED water, that the addition of a 15" 6 blade aluminum flex fan moves a lot more air than the stock fan.

I had a similar problem what I did was drained the whole system than put tap water thru the whole sys. Darned than filled the hole system with a cleaning agent (i.e. house hold cleaner) let that sit over night darned that and then rinsed that out, then I took the heater core out and flushed it with a garden hose and put it all back together and worked grate. Sounds like a lot but the sludge that came out looked just like the ghost from ghost busters the little green thing.

As Baldy says, you have over-cooling without a thermostat, but once the thermostat is installed you have overheating.
So the immediate problem should relate to either the thermostat itself, or air-locks (you mentioned circulation was O.K.) - regardless of the condition of your core.

If it were me, I'd simply run water through the three systems to make sure they're clear, If I had flow at this point I would then fill it with water and Gunk Super Cooling System Flush. Run it for the recomended half hour, drain and flush. Then put in a new thermostat in the right direction. If the guage still registers hot, then I'd replace the sender and gauge. If you do all that correctly, it has to work, period.
That's all there is to the cooling system, no more complicated than that.
Now if every thing is not stock and you have hot rodded the truck, i.e. different engine, radiator, fan, changed the air flow path, etc., then it's anyones guess as to where the problem is.
Where did you find the flex blade Dave?
Denny Graham
Sandwich, IL

may be a dumb question but when you drill the hole in the thermostat do you drill it in the flat part or the "sensor" part and is this the best way to get air out of the system??

Denny..Flex-a-lite fan 15" 6 blade race fan (Jegs) 400-1715P steel spider, aluminum blades...you may have to open up center 7/8" hole to 1". Does it work?...sucked the chrome right off my front bumper! Really!!

Thank you everyone for your responses. I have been away because of family issues and just logged back today.

The truck is completely stock including the 235. I installed the thermostat correctly and it did work when I placed it in a pot of hot water. (It was fully opened by 180 degrees according to the "kitchen" thermometer!

I never tested the heater hoses when the engine was hot. Not sure if the "kitchen" thermometer would read correctly on it anyway. I was always told that if the hose is too hot to hold... its too hot for the engine. When it was running hot, the heater hoses were too hot to handle.

Yes... the hole was drilled on the flat area of the thermostat and it was installed correctly. (I double checked it myself thinking the same thing.. the only "stupid" question is the one not asked!! :-)

My plans are to flush out the entire system and have the radiator cleaned and pressure tested. For now it is resting in the garage and comes out on the nicer dryer days (which seem to be leaving us now here in the Northeast)

Thanks again everyone!!

"I was always told that if the hose is too hot to hold... its too hot for the engine."
I'd say 200° rubber would be "too hot to hold", but definitely wouldn't be too hot for an engine

if you don't trust the kitchen thermometer to check the water temp in the rad, what made you so sure it was accurate testing the thermostat? if you check the water temp with the kitchen thermometer and find it's around 200, you've got an inaccurate gauge or sending unit

the other cheap and easy check is to try a 165 stat and see if the same thing happens ... I've never seen a 235 run hot unless it wasn't getting good water circulation, they're a cold blooded lot

Bill

Did you remove the petcock on the drivers side of the engine to see if that was plugged? 235's have a tendancy to build up rust/crap around the rear cyl which would make it run hot. Open up the drain, if plugged get a coat hanger and go to town. When refilling the block with your antifreeze/water solution, do so with the top part of the therm off, that way you can fill the block and head with antifreeze without air. Then put therm in and reattach hose.

A friend just went thru all this with his 235 , he ended up pulling the head , the small holes were blocked with rust deposit , cleaned and flushed it all and is working much better now.

Dusty has a good point. If you have done all the above and are still having problems then in all likelihood you have a cholesterol issue, rather partial blockage of one of the water jackets.
I worked at an auto parts store when I was a kid, in the late fifties. Helped out in the machine shop, mostly cleaning and assembling.
I saw many passages between block and head that were completely closed from rust and ran into it on many engines I had down for top end work. Other than pulling the head, I don't know of any way to tell if that is you problem short of pulling the head.
Denny Graham
Sandwich, IL

If all else doesn't solve the problem, before doing major surgery on the engine, don't rule out a worn out water pump. It may have enough flow when the thermostat isn't installed, but it may not with it in.

A thermostat doesn't restrict the flow much, but it may be just enough to cause the engine to run hot.

About the only thing that can go wrong with the water pump is bearing go bad or bearing seal leak. That still won't affect the pumping ability much. Of course if the impeller is completely rusted through thats another story,(but I haven't seen that in my 65 years).
Denny Graham
Sandwich, IL

Also check your lower radiator hose spring. If it collapses it blocks flow.

My 261 runs great with a 180 degree thermostat.