The Stovebolt Site Forums The Shop Area Engine Shop over heating 235

Hi All, I got my 235 engine installed and started up after about 3 years. It is a used engine that had good compression and ran good. Before installing it I ran the engine on a test stand and it ran fine. I installed the engine and after getting the engine up to temp I noticed a little weeping from the top radiator hose. I am using reproduction clamps and they are pretty flimsy. The temp got past 210 and I shut her down and she began to spew coolant from the expansion pipe. I notice that the top radiator hose was cool while the bottom one was hot. Does this mean the thermostat is not opening? I am sure it is a new thermostat. Also, the top of the radiator was not too hot and if you made an imaginary line down the center of the radiator it seems like one half was not hot at all to the touch. Once I turned the engine off and it was overheating then everything got pretty hot. Does this sound like a thermostat issue or a pump? It have a new pumps and radiator was cleaned a while ago. I also had done the 235/216 water pump conversion to raise the fan to the center of the radiator. Before this 235 I ran a 1939 216 (with this radiator) and even in 100 deg temp the engine never got above 190. That 216 ran like a watch, albeit at 45mph but ran like a champ. I am hoping better things from a 235.

Hi RC,
If your water pump is working ok (and if it has been sitting still in coolant or water for apx 3 years it might not be), then it sounds like your thermostat. If you're circulating water, have a clean radiator, a working thermostat (I prefer a 160 degree model) and if you don't have a bunch of junk back around the 5 and 6 cylinders (pretty common), your 235 should not have cooling issues. Here in DFW (the waiting room for hell) 100 degree days are common for almost 6 months out of the year. I have an aluminum radiator and an electric thermostatically controlled puller fan with a special shroud. Around here that's what you need to keep it cool in traffic especially.

A couple of things to consider:
1. You may have an air pocket and need to bleed the system. I had the same symptoms, hot on the bottom and cooler on the top. I suspected I had an air pocket and just ran the engine with the radiator cap off (hot enough to open the thermostat but not overheat) . I also bled the system through the radiator petcock.
2. Some people have drilled a small hole in the thermostat to allow a "bleed" through and apparently enhance its ability to open. That also has worked for me.
I'm sure others have lots of experience with this and can offer better advice.
don

Uh..........be sure to check that your thermostat is not upside down. No offense just sayin. Not that I have ever done anything like that myself, LOL. Doc.

I did not think about bleeding the system. I just filled it up with 50/50 coolant and started it up. So I have to run it without the cap until it gets to operating temp but would air pockets prevent the thermostat from opening? I thought it was temperature that opened the thermostat. I looked and see there is a 160 thermostat name Failsafe, which is supposed to fail in the open position. They are twice as expensive as standard thermostats anyone used these Failsafe brands? How big of a hole is needed in the thermostat so it can bleed through?

Failsafe is fine or you can drill a 1/16 hole in the flat edge of your current t-stat far enough inboard to not be blocked by the flange/gasket. The usual procedure is to fill with coolant and run with the radiator cap off until the T-Stat opens and you see coolant moving. The level may drop as the T-Stat opens. You only need about 1/2 inch of coolant over the tubes. This allows for expansion as the coolant heats up, or install a coolant overflow tank.🛠

Personally (for another opinion here) I would not suggest Failsafe. If the engine overheats even one time, that thermostat is forever stuck in the open position. Unless you take it out and physically remove the two locking tabs. Or I have removed those tabs before putting one in. If the thermostat gets stuck in the open position, it is like not having a thermostat at all, and I don't like that option. Most thermostats sold today have a jiggle hole or bleed valve. Before you purchase one, look to see if it does in the product details.

I agree on the problems with the fail safe design.The 216 on my truck must be burped when I refill it with coolant. It will never recover by itself. I open the heater hose connection at the thermostat housing and close it after all the air has escaped during filling. The 216 in my 38 does not present this problem.

Leaving the rad cap off on an unpressurized system will not change anything.

In regards to this subject, is it advisable to put an overflow tank on my 54-3100 235? Doc.

If you live in the South (which you do), the answer is yes. An overflow tank does a few good things. When your radiator gets hot it will burp coolant into the tank and then when it cools, all that coolant will go right back to the radiator. Prevents an air pocket and reduces air bubbles (which you really don't want...fluid does a much better job of transferring heat), gives you a little more coolant in the radiator (which is good--more is better) and makes it really easy to see the level of coolant and to safely and easily add more if needed.

Thanks Jon G, I was having a similar problem. I don’t have a coolant tank next to my radiator. And I would always notice coolant on the inner fenders. And now that you say that the radiator burps. This all makes sense to me. Going to install a coolant tank.
Awesome
Thanks so much
Elmo

Guys, thank you. I think the problem is solved. I did what you recommended, I open the radiator cap and waited until it came up to temp and saw that the coolant was moving around in the radiator. I put the cap on and it seems to run right at 185. I do not have a coolant tank but I may add one any one have pictures or part numbers for such a tank?

Hello by chance are you going to sale the 216 chevy engine ? I am in need of a 216 engine.. Thanks

I took old pieces of a truck seat and formed the bracket which I mounted to the 3 screws (heater motor cover). This has worked great. Before it would puke on my fender well and draft tube.
Todd

I had a simular problem on my 54 235 but it was because the radiator had set for 2 years with stop leak in it. I had bought a new radiator but used the antifreeze from the old radiator that had stop leak in it. I ended up buying a high flow aluminum radiator. No problems in the last 12 years and I take it on 1200 mile trips in the summer.

Southwest I've a 216 i dont need 719-205-2203

Southwest I've a 216 i dont need 719-205-2203

I have a '58 235 that was overheating with in 15min of idling. I tried everything I could think of. I replaced the thermostat 3 times and replaced the radiator with an aluminum one. I pulled the water pump out for the 3rd time to inspect it again, and this time I bought a new one. I noticed a hole on the new pump I had not noticed on the old one before, then I looked at the block and the hole was barely noticeable, so I picked out the hole and found it was full of crud that came out and made a passage up into the head. Make sure yours is clean.
Cleaned it out and problem solved.

As you can see from the pictures this hole in the block behind the water pump must be clean and clear, run a piece of bailing wire up and down inside of it all the way up into the head to make sure it's clear and as you can see from the pictures my water pump was plugged up and I didn't know it and that was causing a Non-Stop overheating problem, even in the winter.

rc356s Might be a mouse nest in the block,watch for trash,if you change thermostats fill the block up and put your thermoststat right in the fluid bolt on your gooseneck and hose top it off. One water pump test...take upper hose off radiator stuff rag in radiator fill hose up have some one start engime if it throws water out in the yard probably OK. Use water cheaper.

Shaffers 1950 That is a good job !! Iwant sdme oil jars...haveb't seen em (for real) since 1966 in westport ill. near Vincennes I ndiana