The crockpot cleaning method is great for removing burnt on fuel residue. If the engine is just a blob of mud and grit then clean all that off first. The antifreeze will not remove grit from bearings. The engine should be taken apart before cleaning. If left assembled even loose bits of residue can get into bearings. Other than burnt on residue all other dirt can be washed off without the need for soaking in hot antifreeze.

Ed S