Pressure in Coolant Tank

Could be air compressor

 

Head gasket can still blow without causing oil & coolant to mix -- it just depends on where the gasket fails

 

From what I been told its gear driven and has coolant that runs with it? But if the seal it worn it could cause air to build in ur tank

 

Get the system pressure tested or buy a test kit for head gasket. Got mine from nappa $80

 

Theirs a coolant channel that goes through the air compressor to keep it from overheating. When the compressor fails it will pump all that compressed air into your coolant system therefore pressurizing it to 120PSI or as close as it can get it.

Quick way to test that is to pull the main line off the air compressor and drain the tanks completely while doing the bottle test on the coolant overflow hose and see if the bubbles persist.

 

Wouldn't that be really loud with that line off lol

 

Well for starters, cooling systems are supposed to be under pressure (like 5-8 psi). The only time its an issue is if it is over-pressurizing from a blown head gasket or failed compressor. It will be noticeable as in there will usually be heavy bubbling in the header tank. If the coolant is discoloured, I would have a combustion gas test done on the cooling system for starters.