Late (53) flathead. New issue. A month or so ago, started it to move it. Was running for about 5 minutes or so, and notice a pool of coolant. It's puking through the overflow. Car is not hot, just barely warmed up. Open radiator cap and there's above normal pressure. My first thought is gasket issues, with exhaust gas getting into the cooling system somehow. Anybody seen this before, know a place to place to start?
Could be a sticking thermostat. To tell if it is a combustion leak, remove the thermostats and the fan belt temporarily, and leave the top radiator hoses disconnected. Fill the thermostat housings on each head to the top so you can see the coolant. Start the engine and look for bubbles. You can run it that way for a while as long as it doesn't overheat. Sometimes you have to rev it a little to see the combustion leak, because at idle there isn't as much cylinder pressure.Hopefully its just a stat.
I don't know what it is and usually blame the head gaskets first but the cooling system on a flathead is two separate systems and are only connected by the radiator. Also you have one heat guage showing the temperature of the coolant for both sides, supposedly. You could have a stuck thermostat and the heat guage not hooked to that side or the sending unit not functioning. Also doing what Thunder describes above will help narrow down which side is the problem. Neal
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