jaf7081

OK, I will make a long story short here. I pulled the head on my 97 4.0 and I wasn't thinking and did not drain the coolant from the block. So the coolant collected on top of 3 pistons inside the cylinder. I knew I would have to clean that up, but when I went back to it about a week later, the coolant was gone out of two of the cylinders. Does that mean the piston rings are leaking? Do I need to rebuild the engine? Thanks.

98 JeepJeep

The rings will never be "air" tight,even on a fresh rebuilt motor the rings are still gapped. just because it didnt hold the antifreeze in the cylinder doesnt mean anything.

jaf7081

Thank you, that was what I was hoping to hear. I really don't want to have to do a rebuild just yet on this engine, mainly because I do't want to have to pull the engine. I feel confident that I can pull it, just not so sure about getting it back together again! What do I need to do to clean up the engine from the antifreeze I got everywhere? I am picking up the head from the machine shop tomorrow and hope to get this thing running by this weekend.

98 JeepJeep

when i did my engine i used break cleaner to clean the deck and cylinders and also fine sand paper to clean up the cylinder walls.

XJ4MEPLZ

If you haven't turned the engine over you can drain the oil and most of the coolant should come out. You may want to run cheap oil for a little and change it out again with a new filter.

Coat the cylinder walls slightly with oil, this will burn off but prevent oxidation when you clean the metal surface.

jaf7081

Yeah I have not turned the engine over, so that is what i thought that I could just drain it. Do I need to pull the oil pan or just drain it like normal? I ran synthetic oil in it, and I have heard that you should not go back to regular oil after running synthetic unless you do a flush. Is this true? I only ran synthetic for about 25 miles before I figured out that the used engine I had just put in the jeep had a blown head gasket.

98 JeepJeep

just run cheap oil for a few hundred miles and changed the oil with the motor HOT..this alows the oil/antifreeze mix to be thinner and drain....otherwise it forms a thick sludge coat.