Classic/Antique Car Repair: Operating Temperature, Over heating causes

Question
Hi Robert

I have a 1939 Buick Model 40 with a new radiator, new water pump, and newly rebuilt engine. I am running 50/50 mix of water & antifreeze

When driving, at 40-45 MPH it settles at approx. 200 degrees

When driving 50-55 it settles at approx. 220 degrees

Should I be concerned?

Any insight would be great

Thank Much!1

Answer
Beautiful car, Mike. Sorry you're having problems.

Your car does seem to be running on the high side, temp. wise. As you're aware, there's a myriad of reasons for overtemp. I'll just run through a few you may not have thought of but oftentimes there certain tenancies for certain engines. I'm not a Buick expert so if all else fails, consult with you're local Buick Owners Club. I'm sure someone there has some specific experience with your problem and engine.

Here are a few things to check that you didn't mention in your note:

Do you have a thermostat installed and/or is it functioning? As in other parts of this message, just because it's new, don't necessarily assume it's good! An inadequate thermostat  will increase coolant flow reducing it's ability to conduct heat. Alternatively, I had a '41 Cadillac with thermostat controlled shudders in front of the radiator. They were partially open when hot causing high engine temps.  

Does your engine have an overbore from stock? Overbored engines tend to run hotter due to thinner cylinder jackets.

Have you confirmed that both radiator and engine water jackets are clean and not blocked? I've seen a lot of residual scale left even in engines that supposedly have been "boiled out".

Is coolant full? Sometimes there is trapped air in the system that reduces the amount of coolant. Similarly, even if hoses are new, check for partial collapse during operation.

Check timing. Retarded timing can cause an engine to run hotter.

As you can see, over temperature can have a Pandora's box of causes. The preceding are things that either I've personally experienced or read about others experiencing. And as I suggest, don't necessarily assume that new is trouble free. I've seen new parts out of the box be bad. You simply need to be methodical checking things and ask the Buick guys for specialized help if these generic faults don't pan out.

Best of luck,

Bob