Help: Bubble in Radiator

[lqy125]

94 Explorer with 180,000 miles, overheat and see air bubbles when open radiator cap.
Questions: Is the engin head gasket problem, how to know which side is the problems, is there a way to isolate the cyliner?

Thanks for help!

 

[shamaal]

Cylinder head compression check. Write down each readings, the one's that are out of family identify the problem.

Or you could remove the plugs and look for the fouled.

this of course assumes that you have no coolant leak.

Good luck, do some searches and ask questions.