Overheating Flathead
 

On my ‘35 flathead I’m having problems with overheating. I can drive it one weekend 20-30 miles and it will never overheat then the next weekend it will run hot to whole time. I had the radiator checked, flushed the engine and use distilled water with water wetter. Why is it not overheating all the time and why does it overheat out of the blue. I need help!

Re: Overheating Flathead
 

loosing water? white smoke out of tailpipe? overflowing the radiator? pressure system? take cap off run engine until warm, make sure the water level is above the fins and below the cap, put the cap on and then take it for a run and see what happens

Re: Overheating Flathead
 

Hoses collapsing, bad thermostat?

Re: Overheating Flathead
 

Blows the water out of the overflow tank, no pressure cap and I keep the water just above the fins. The hoses are new and no thermostats.

Re: Overheating Flathead
 

Re: Overheating Flathead
 

Are you using thermostats? Sometimes a thermostat might not open, or only open part way - causing overheating issues like you're talking about.

Re: Overheating Flathead
 

Also check coil

Re: Overheating Flathead
 

How you drive it may be a big factor. Many early Ford V8s do not like idling for long periods of time, particularly after a good run at speed. Does your car cools acceptably at 20 to 45 mph, but not when you drive faster or slower?
What temperature does it run when it is not overheating?
How hot is the ambient temperature for each drive?

Re: Overheating Flathead
 

Are you running a mechanical fan, or electric ?



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Re: Overheating Flathead
 

Bite the bullet and remove the radiator and take the top tank off , then you can make sure you have no blocked tubes.
Lawrie

Re: Overheating Flathead
 

I agree with Lawrie's advice. A San Antonio friend with a 36 recently fixed the overheating problem on his car. He had the radiator cleaned, cleaned the block with dilute phosphoric acid then with baking soda solution, and installed Skip's high flow water pumps. Each step helped, but didn't solve the problem. Finally he took the radiator to a different shop, had the tanks pulled and the core rodded out, and that solved the problem. I test drove the car on a 98 F day with no overheating on an extended run last month.

Re: Overheating Flathead
 

Check to see if you might have combustion leaking into the cooling system. I had this happen on my '35 in 2019 on my way to Auburn Indiana. Turned out to be a blown head gasket.