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Mark's 37 · 09-09-2015, 09:14 PM

I haven't done this with a flathead but did these tests for many years as a Ford mechanic. If there are combustion gases in the cooling system from either a leaking head gasket or a crack somewhere these 3 ways of testing work well.

1. Install a radiator pressure tester on the radiator and watch the pressure gauge while running the engine at idle and at fast idle. If the pressure gauge needle begins to climb, pressure from cylinder compression is leaking into the cooling system.

2. I have used this tool many times. Follow the instructions carefully. Lower the coolant level enough to be sure the coolant isn't sucked into the fluid chamber of the tester. If the tester fluid changes color according to the instructions, there are combustion gases in the cooling system.
http://www.summitracing.com/parts/oe...7XcaAstW8P8HAQ

3. The easiest way, if you have access to a Smog Test machine, is to again lower coolant level a few inches and with the engine running at operating temperature, check the CO/HC level with the Smog Machine probe sitting just inside the radiator without touching the coolant. If CO/HC level goes up, same thing, combustion gases in the cooling system.

09-09-2015, 09:14 PM	#23
Mark's 37 Senior Member Join Date: Jul 2015 Location: Aptos, Ca Posts: 355	Re: Foaming/cavitating coolant in my 34 I haven't done this with a flathead but did these tests for many years as a Ford mechanic. If there are combustion gases in the cooling system from either a leaking head gasket or a crack somewhere these 3 ways of testing work well. 1. Install a radiator pressure tester on the radiator and watch the pressure gauge while running the engine at idle and at fast idle. If the pressure gauge needle begins to climb, pressure from cylinder compression is leaking into the cooling system. 2. I have used this tool many times. Follow the instructions carefully. Lower the coolant level enough to be sure the coolant isn't sucked into the fluid chamber of the tester. If the tester fluid changes color according to the instructions, there are combustion gases in the cooling system. http://www.summitracing.com/parts/oe...7XcaAstW8P8HAQ 3. The easiest way, if you have access to a Smog Test machine, is to again lower coolant level a few inches and with the engine running at operating temperature, check the CO/HC level with the Smog Machine probe sitting just inside the radiator without touching the coolant. If CO/HC level goes up, same thing, combustion gases in the cooling system. Last edited by Mark's 37; 09-09-2015 at 09:22 PM.