I have a 98 xj, 4.0 I6. I was haveing some problems with my cooling system and after a little digging I found that I was getting exhaust gasses in the fluid. I ordered everything to change out all the gaskets and a new head from clearwater. Since I can see a lot of white build up inside the head through the t stat hole I figured it might not be a bad idea to swap it even if the problem was just the seal.

I got the head off and I don't see anywhere that could be leaking into the cooling system. The oil wasn't gunky and the valve area actually looks like its in pretty good shape, and the spark plugs look ok (though the PO said he changed them and I haven't had it long enough for them to show indications of much.) There also isn't any visible coolant in the cylinders. The water jacket holes are super clogged so maybe that caused a failure with out the gasket actually cracking? Is it possible that one of the cylinders has a crack in it below the piston? If so how would I check that?

I think the most likely answer is that there is a cracking the head somewhere and I just didn't see it.

Thanks for any advice you guys can give me.

 

You won't necessarily see it. My head gasket gave out two years ago and I never did see where it leaked. I could certainly see the results, but I could not find a smoking gun. I replaced the gasket and it ran fine right up until March when a Suburban pulled out in front of me.

I suggest you just slap your new FelPro gasket on there and call it good. I'd also do a chemical flush of that cooling system once you get it back together. Since it's warm weather, you can run just that for a couple of weeks with no expensive coolant in it to get in the way of the cleaning.

If it turns out you have fatal problems, well, at least you didn't spend money on coolant.

EDIT TO ADD: I just read through my thread again, and I recommend you read all the way through. I think you'll find it worth your time. Lots of good advice was given.

One more thing - do yourself a big favor and replace your water pump while you are in there.

 

It is most definitely possible to have a cracked head that you cannot see, it would need to be magna fluxed or pressure tested to find it. If you already have another head, put it on. If the problem is in the block at least you already have the head purchased.

I believe that my head gasket is blown between #2 and #3 cylinders,,,I think I will be getting another head too,,,

 

Thanks for the input guys, much appreciated.

I already had the new head so I threw that on, torqued everything to spec in the correct sequence. That back bolt is a serious PITA! I didn't put any oil in the cylinders which I probably should have done. The only real issue I've had is I seem to have a small exhaust leak. It's really hard to see but it looks like it's coming from the back part of the engine, I'm thinking i need to double check the manifold bolts since there are a couple back there that are hard to get to let alone get my torque wrench on.

When that's sorted I'll do another exhaust gas check.

Mark, I actually just changed my water pump right before this so that's good to go. My jeep no longer sounds like a diesel either, gotta love the new lifters! Sorry to hear about your accident, I've had a similar experience with a mini van and my old F150.