Polse7317 wrote: ↑Tue Jun 12, 2018 8:59 pm
I have a over heating engine and overflowing coolant after +- 20 minutes running .
IMHO, there could also be other reasons for your problem worth investigating:
1) Is your car fitted with the CORRECT thermostat? I'm not referring to its temperature rating, I'm referring to its physical format. Does it have the sleeve that closes off the bypass port? (Its that long vertical slot behind the thermostat). For the '65 I worked on it was C3731. This bypass circuit is intentional and is meant to allow fast warm-up of the engine, but when the thermostat opens, it should close this bypasss circuit off, forcing all coolant through the radiator, unless you also have the next problem:
2) How much coolant can escape from the pipe inside the header tank via the hole for the otter switch and flow UNCOOLED via the "filler pipe" on RH side of the header tank to the COLD side of the radiator, thus creating a second UNINTENDED bypass circuit. On the '65 I worked on, this second bypass route also allowed a significant amount of coolant to bypass the radiator. I installed a "plug" in this hose with just a tiny hole in the top to allow air to escape back to the header tank -but blocking any significant coolant flow. In my case the "otter switch hole" was so large, this very hole is now also used for filling the cooling system.