1994 Lexus es300 3.0L V6. I removed the EFI relay so I could crank the engine without it starting. This was done after the car had sat all night and the engine was cold . After cranking for a very short time I got out and removed the radiator cap. As soon as I removed the cap it had a lot of pressure in the system and blew out cold antifreeze everywhere. Is this a sure sign of a head gasket problem? I don't have any of the classic signs other then once in a while it will blow antifreeze out of the overflow tube. Am I missing something? Any help is greatly Appreciated. Thank you very much in advance.

 

Yes, that's a very strong indication. You can do a "glove" or "balloon" test on the headgasket, removing the cap and putting a latex glove on it. Plug the overflow line and crank.

If you take the plugs out, you can install one at a time and identify the problem cylinder(s).