You should eliminate the gauge as a problem. Search here on "comp board bypass" and see if you're up to it. There are a couple of methods. I just take a short loop of wire and press it on to the 2 pins. It's not too bad a job. Mostly takes patience.

I'd also want to verify that I had the correct thermostat. If it doesn't have a bleed valve or the valve is at the bottom, you could be trapping air.

You could do the above yourself. You need a large drain pan, screwdriver, 10mm socket (or wrench in a pinch).

Consider getting a Haynes manual. 240s are easy to work on. Folks here seem to prefer the Bentley manual. I have both but use the Haynes more.

The foaming bit is new to me but let's assume the anti-foam is helping.



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240 drivers & parts cars - Ohio