the only way to be sure is to perform a test called a leak down test. you can buy testers to check for combustion gases in the coolant but they are inconclusive in many cases.based on the info you have provided my first thought would be a head gasket.but you would need to take it to a shop and have the test done to confirm.

Answered by homer1967 (expert)
415 answers provided

That was my first thought,but can't run tests...doesn't start right now.....and I am kind of working on several problems at once. Had a bad coil, so replacing. Hard starting problem, so have ignition module off to be tested and other ignition parts. I was contemplating the ideal, if I was going to take off the head, that I just replace, because of the miles on the vehicle?? (Full head with valves and guides) What do you think??

Response from chevymwernsmann
1 question asked

It's probably good that it won't start. You are just going to do more damage if you get it started anyway. have it towed to a shop for diagnosis.

Answered by Wrenchtech (expert)
14,716 answers provided

yes that is the best thing you could do.you do not want to try to start it or keep cranking on it,because if you do have coolant getting in your cylinders you could hydrolock your motor.

Answered by homer1967 (expert)
415 answers provided