high pressure in cooling system
 

I'm wonder if anyone can help diagnose high pressure of gases in cooling system.
Car is running great, still after approx 100 miles on HWY temp is going up.
I can't see any oil in coolant or coolant in oil system. Still there's very high pressure of gases (air?). To be more specific, driving on 5th, 100m/h is not a problem, only as soon as i idle engine, temperature is going up. accelerating will bring tmp down again. When engine stop, there's a lot of spill from overflow tank and i can release a lot of steam from radiator!. When engine is cool, coolant from overflow will go back to radiator.
There's not "white" smoke from pipe, no lost power.
one more: on old engine i have "burbling" noise in core heater. This sound didn't go away when i installed new engine two years ago.

Any ideas?
BTW When it happed first time, i replaced thermostat.

Your head gasket is leaking. Actually, the head gasket is warped around the exhaust side cooling passages.

But you don't have to take my word for it. Run a block test to confirm

test
 

how i can run block test? just cylinder pressure?

Bhg
 

No. Have a shop perform it. It is a special liquid that is used at the radiator top, and can tell if gasket is blown.

OR/AND....the radiator top can be sniffed by an exhaust gas analyser. Hydrocarbons means exhaust gasses in the cooling system....means BHG.

PS: Your symptoms are exactly what mine were, $800, my labor, 2 1/2 yrs ago.