Classic/Antique Car Repair: 1930 Ford Model A Roadster, head gasket problem, combustion gasses

Question
Hi Jack,

My grandfather owns a 1930 Ford Model A Roadster originally from Canada which has the standard A motor here in NZ, we recently installed a brand new radiator in the ol girl which was from the US of A. Since the installation of the radiator we've had a problem that we haven't been able to cure. Which is why I'm emailing you.

Basically what's happening is the radiator is overflowing with white foam from the coolant and water. Several people have said it's a cracked head, but we've done a compression test serveral times which were fine, there doesn't seem to be any traces of oil in the water or water in the oil. We've tried several different coolants and tried mixing less leaving the same result..foaming. The only time it got a little bit better but still boiled over was when we put straight water. There's also no water leaks either.

The only time it foams up is when you climbing a hill in 3rd gear (doesn't do it in 2nd even when the motor is revving) and when you are on the motorway travelling between 40mph plus.

The only other thing we have thought of before we take the motor to pieces is the there maybe a crack in the head that is expanding when the motor gets hot and is sucking in air or it's some how sucking in air through the shaft of the water pump.

If you have any ideas your input would be much appreciated.

Look forward to your reply.


Kind Regards,
Owen Jones

Member of the North Island Model A Club of NZ
http://www.modelafordclub.co.nz/

Answer
Since this only happens when the engine is loaded and pulling hard, I think this probably is a head gasket problem or a crack in the head.

A compression check will only find leaks that are present when the engine is not running.   The test you need to do is for combustion gasses in the coolant.  

You can buy a kit that will check for this at an autoparts store - Balkamp is one firm that makes these kits.  The kit contains a special chemical that you expose to the hot coolant and watch to see the color change in the chemical.  If you have what I suspect, it will show up in this test.  A professional cooling system repair shop should be familiar with this test kit.

The water wouldn't foam unless there is something other than coolant mixed in with it, and it has to be more than just plain air.

There is a vacuum at the water pump lower hose inlet at high rpm, but that would mean the problem would show up worse when you climb the hill in second gear - and that isn't what is happening here.

Best of luck to you - these are great cars, especially where you don't have to deal with crazy people driving 90 MPH on the freeways!

Dick