Combustion chamber leaking into coolant test

[aloharovers]

How can you test for this?

I dont have any oil in the antifreeze nor coolant in the oil.
Not loosing any coolant.

But tonight I went out and started the engine to bring the truck into the garage. Was running 5 minutes tops while I removed the cb antenna.

I am putting a bigger radiator in. Shut down the engine and started to take off the rad hose clamps and water started spraying.
System was under pressure. Not max like when hot, but definatley 5-10lbs.
Rad was just barely warm to touch, like 100*. I didnt measure.
There isn't a t-stat in right now. Could this contribute?

I thought that the system only built up pressure when the engine got hot.

So I am now worried that I have a leak in one of the combustion chambers into the coolant jacket.

Checked compression and its good in all cylinders.

Any way to test for this?

Thanks

Pete

[NH2112]

If you don't see bubbles in the overflow reservoir with the engine running, then you probably don't have any combustion leaks. You can also remove the water crossover and run the engine, this way you could pin it down to one bank or the other. Lastly, you could rig up an adapter to pressurize each cylinder with shop air through the glow plug hole and listen for bubbling in the radiator.

[ZZ]

My 6.2L starts building pressure a minute or two after I start it cold.

[aloharovers]

Originally posted by NH2112:
If you don't see bubbles in the overflow reservoir with the engine running, then you probably don't have any combustion leaks. Hoot, thats good news. I haven't got any bubbles and I am not blowing the radiator cap at all. Even when its 230*

ZZ thanks for that, glad to know its common.

Pete