1966 Olds 442 with a 400 BB that has had major rebuild with plenty of upgrades. Problem is is that the car after running for sometime (driving. it seems to not overheat on idle) the car will start spitting out antifreeze from the overflow hose. Im not seeing any oil in antifreeze or vice versa. Ive just replaced the thermostat with a lower temp (160) higher performing thermostat....still getting the same issue. Temp gauge is reading 170 (could be faulty). Any ideas? Looking to go with a higher performance water pump but i just noticed that the radiator cap isnt as snug as it should be...could this be the cause? Newbie to the land of Olds so any help would be appreciated.

Rad caps are cheap, that would be a good start. And just FYI, just because there is no oil in water, or vice versa, doesn't mean compression isn't leaking into the cooling system. Do a compression check. Also do a radiator pressure check. Watch for falling pressure readings.

Hi hrazor35, hello everyone,

Welcome to TOC.


Yes, an Olds 400 would be a BB.


If it was done right, it should not overheat.


Without further evidence, there is no reason to assume a higher than normal temp.


You have your answer, it's not overheating.


And you have identified the cause of your coolant loss.


Make sure it's the correct one for your application, and that the mating surface in the filler is clean.

Regards, Norm