My car had oil in radiator now it will not start?

Hello, if there is a head gasket leaking really badly or a crack in the engine block, it's possible the engine is hydro locked. What you can do is remove all the spark plugs and try cranking the engine over. If there is a cylinder filled with coolant it will come blowing out of the spark plug hole. And the engine should turn over again, but at this point don't force the engine to turn over, you can bend a connecting rod or worse, at least if you clear the cylinders out, and the engine turns over, you'll know what's happening and can decide what to do from there.

https://www.2carpros.com/articles/head-gasket-blown-test