The Stovebolt Site Forums The Shop Area Engine Shop 235 overheating in my 56 Chevy

Hi all
I’m new here and have been perplexed by an issue I’ve been battling since last year. I own a 56 Chevy 210 with a straight 6. Car runs good, but can’t get the thing to stay cool. It has a new water pump, radiator, 6 blade fan, rad and heater hoses, thermostat. It will get to about 220 before the thermostat opens up and then it usually comes back down and stays ok for the remainder of a drive. Timing seems ok, didn’t do compression test but I don’t think it’s the head gasket (although not sure yet) my friend had a combustion leak tester kit and did that without any issues detected. Would love some help to get this solved once and for all!

First, thank you for fessing up to working on a car. As you know this is a TRUCK site. Does that mean we won’t help you? No! There are a couple of things you can try. You may have an air bubble in the system keeping water from getting to the thermostat to open it. Burp the system and see if it takes more coolant. Second pull the thermostat and drill a 1/16-1/8 “ hole in the flat flange to allow a small amount of coolant to bypass all the time. Finally, if you have any more CAR questions post them in the Greasy Spoon forum which you can access after you make 5 approved posts.🛠

"It will get to about 220 before the thermostat opens up and then it usually comes back down and stays ok for the remainder of a drive."

Get a new thermostat, 160-180 degrees
http://chevy.oldcarmanualproject.com/chevyresto/56051.htm

Drill a hole in it as described by Martin

At what speeds does it run hot: above or below 40 mph?

I apologize about posting here! My mistake, I’ll make sure future questions go in the appropriate forum. So I did drill a 1/8 hole in the flat part and did change the thermostat several times to no avail. Even tested them in a boiling pot of water and confirmed that they open. I’ve tried flushing the block a bit too but maybe I’m not doing it correctly

You are welcome to ask any engine/drivetrain related questions you may have as they are similiar or the same in some cases to our old trucks, but yes we are a Chevy/GMC truck site for pre-1973 models.


If you have old Chevy car specific questions, we recommend these sites :



chevytalk.org

They have a 1955-57 section... and they have some knowledgeable folks over there.



VCCA Chat - vintage chevrolet club of america, forums

You do not have to be a member to use most of the technical forums... good place to visit.



Also, for the engine and driveline there is :

Inliners.org

which is for all makes and models of inline engines... lots of knowledgeable folks about the chevy sixes over there as well.


Welcome to the 'bolt... maybe someone can get you sorted out.

-Woogeroo

When it heats up, if you have a heater, turn the control to hot. This should should shoot a shot of extra water into the system. If it does the temp will drop. If this happens you know you have a bubble of air in the system.🛠

Brymcfly13,
If you suspect you need to flush your system, rather than just opening the Drain-cock, I removed mine during flushing
because only opening it creates a very small passage. I temporarily removed mine and it flowed like a river after a couple
of shots of compressed air at the opening.
good luck, Jim

I agree with the guys about trapped air in the system.
I had a 235 doing the same overheat until I pulled the thermostat and poured coolant right into the engine. It took nearly a gallon!
Once I buttoned it back up, fired it up and ran it with the rad cap off and filled it too. Once the thermostat opened (you'll know when it does by the sudden increase in coolant level) cap it and drive it.
Your car may not have an overflow tank, so don't worry about a low coolant level in the rad when it's stone cold because it will self regulate the amount of coolant it likes.

Sorry I’m a bit confused . When I open the thermostat housing the coolant level is right up to the top of the thermostat

Does the car have a heater? If so, make sure coolant is flowing through it during warmup. It will keep the coolant circulating better than any drilled hole could possibly accomplish. If there is a manual valve or a petcock like some engines have, be sure it's in the "open" or "full hot" position. The fact that the temp gauge is going up tells me it's not a situation flushing will help- - - -the coolant is getting hot enough to move the gauge, but it's not flowing past the thermostat fast enough to prevent a temp spike.

BTW, if the coolant isn't boiling and forcing the radiator cap to vent, the engine isn't getting hot enough to do any damage. What pressure radiator cap are you running? A 7 PSI cap was probably the original equipment item, and that will allow the cooling system to go to 233 degrees at sea level before it boils.
Jerry

I did run the heater and it dropped the temperature down gradually from about 220 to 200 but it’s still running too hot. It has boiled over a few times in the past

Have you determined if the radiator is functioning properly? I had a radiator that appeared to be flowing properly but after some testing it was found to be mostly clogged. A simple gadget such as an infrared thermometer may help you solve your problem.
https://www.amazon.com/s/?ie=UTF8&a...d-35513078482&ref=pd_sl_3luinef3zz_e