There is antifreeze in all 4 cylinders; the engine is hydrolocked. No antifreeze leakage or bubbles in the radiator, does not smoke, has never been hot, oil is fine, compression is great. Could this be something other than a head gasket? Just recently inherited the car and I am not familiar with the engine. I drive a Ford Diesel.

Any info would be much appreciated.

 

Remove sparkplugs, does the engine wind over?

 

Yes it does.

 

Time for a compression test, TK test, & pressure test cooling system for leaks, then crank over engine & look for geysers leaving the cylinders.