Bubbling in coolant overflow tank

[Hal O'Peridol]

I test drove a 1985 M1009 today. No fast idle, but ran well once warmed up.

After completeing the ride I heard a loud bubbling coming from under the hood. Popped the hood and found that it was coming from the overflow tank. This was happening even with the engine off, so I don't think this is a cracked head/block or bad head gasket problem, also oil was not milky at all.

Bad water pump? Stuck thermostat? Something less easy and more expensive?

My current M1009 does not do this. I DID notice that my M1009 valve clatter is MUCH louder than the one I test drove.

 

[DIESELGREEN]

Could be simply a bad (weak) radiator cap. It still could possibly be internal, I had a civvy scottsdale with the 6.2 that did the same thing. It would stop about a minute after I shut the engine off. Turned out to be compression in the cooling system due to a bad head gasket.

 

[mobileauto2000]

Put your nose down in that recovery bottle and give a good sniff. Dose it smell of exhaust? You will get water in the oil only if the head gasket blows across a oil drain back port.
I'm probably telling ya things you already know, That's my specialty. Just ask my family.

 

[WillWagner]

Maybe a cap, maybe was just over full and was finding it's own level. Don't fill the rad and drive it again.