M60 cooling system bleeding issue

[WYZEUP]

So i am getting to the end of my build. Well im hoping......



So i have pieced the cooling system all together, custom alloy expansion tank, feeding into the rear crossover pipe, z3m radiator, 80 degree thermostat, everything was new when i put the motor back together.



Motor is a m60b40.



Have filled coolant from tank and once thermostat opens blows water out like a whales blow hole.

Tried filling from the top radiator hose and blowing onto the top hose to try and remove air....still does is.

Checked thermostat vent is at top put all back together, filled through reservoir, blew through feed tube from radiator to resesrvoir still a lot of pressure.

Is only when thermostat is open?

Anyone had experience with m60 cooling systems? i dont want to think the worst of it being a headgasket, there doesnt seem to be any mixing of oil & water but im also no mechanic....



if anyone could shed some light would be a massive help, is one of the last hurdles before i can start test driving

It has been suggested to me to check the system with the thermostat removed to eliminate the fact it may be anything else in the rear of the motor??

[36brua]

can you post a pic of your rear cross over pipe and expansion tank plumbing ?

[The Dark Side of Will]

You can use a compression test adapter to push pressurized air into a cylinder.
If you do this for each cylinder, you'll definitely rule out or positively diagnose a failed head gasket. A head gasket that failed from the cylinder into the cooling jacket will push a big fountain of water out of the expansion tank.

Did you ever have heads off this engine?

[WYZEUP]

I havent got any pictures of crossover pipe but have run expansion tank into same inlet factory tank fed into. have blanked all other outlets on the crossover pipe off so only thing that feeds into crossover pipe is expansion tank.
no heater connected.

I was considering getting a block tester and testing for exhaust gasses in the cooling system, the heads didnt come off this motor as it seemed quite well intact

im also thinking it may possibly be just normal as i removed the thermostat and it still did it but only once the temperature got to the half way mark on the gauge so am considering the fact that it is just the water boiling?