Apparant overheating

I have a 1980 Model A built by Shay for Ford. Ford supplied all the running gear hence it has a 1979 Ford Pinto engine (2.3 Liter) and a vertical tube radiator with expansion tank on top.

It has 5800 miles on it.

The problem seems to have started about the time I put new antifreeze in it. It will idle all day at low or high idle and maintain normal temperature, but as soon as I drive it even slowly, the temperature climbs to hot and when I stop or idle it imediately comes back to normal. It has a new thermostat, Checked the cap at 13#, new lower hose and I have removed and checked the water pump to find the impeller tight on the shaft and looking like new. I refilled to the water pump level, assembled the water pump, filled to the top of a 4 inch hose onthe water pump heater hose connection, attached the heater hose, filled to the thermostat opening, assembled the thermostat and housing, filled to the top of the heater hose connection, connected same, filled until antifreeze came out the connection for the carb heat (this connection is on top of the heater line that rus at the top of the cam cover), connected same and topped off the radiator. All this was done with the front end 12 inches higher than the rear.

Previously I tried removing the temperature sensor with the car level, allowing some antifreeze to run and reinstalling. That didn’t help either.

It acts like an air bubble, but if it is, I sure haven’t been able to get rid of it. I have been running it in this 12 inch elevated position for several days and it still does the same thing. Although it now appears not to be getting as hot. It now goes to the top of the normal(?) blue band insead of all the way to the top and idles a little below the half way point.

Any ideas??


It has never “boiled” over

I agree, sounds like an air bubble. Could the bubble be in the heater core?

What is the temperature of the thermostat? I noticed that thermostats come in a range of temperature settings. If it is too hot (195 deg or 215 deg), that would explain it. Also, if the radiator is slightly clogged, and coolant cannot flow through properly, this would also cause it. A radiator shop should be able to flow test the radiator.

The heater is under the seat, but I would think that the way I filled the system progressively with the upper line open that it couldn’t be there, but??

Maybe I can open that small fitting that goes to the carb base again and see if I get any air. That is at the highest point of the heater lines and heater.


It is a 192 with a 13# pressure cap. The radiator is virtually new and looks it inside and out. I’m still inclined to go with the air bubble. I understand this is a common problem on some of the Ford engines of this vintage. I just don’t know what else I can do to get rid of it. It did cool well before. Karl