A little background. I bought the 06 LJR a little over a year ago. I didn't have a lot of background on it, but it seemed to be in ok mechanical shape other than needing a refresh on almost 20 year old parts, as most of the Jeep looked like it still had factory parts on it. A few months into driving it I noticed a slight tick/knock on 1st startup up that would quickly go away. Fast forward to this summer and that noise got a lot worse, and though quieter once the engine was hot, was still audible. After a lot of research and watching videos from Dex Jeeps I concluded i must have some cracked piston skirts. I didn't believe I had broken a skirt yet, but wanted to be proactive to not get to that point and damage the block. I decided to do an in vehicle piston, ring, and rod bearing replacement.
I got it all apart on Saturday. The first thing I noticed was the carbon buildup was very bad in the intake manifold, and top of pistons down into the 1st ring. I also think the head gasket might not be factory, It was a MLS gasket, but it had blue sealing residue around the openings that I don't think is factory, but maybe I'm wrong. Once I got the pistons out I found the piston skirts intact with no visible cracks much to my surprise.
What I did find was evidence of very bad piston slap on all of the cylinders. Surprisingly, the compression (non-power) side of the pistons had more evidence of slap than the thrust side (camshaft side). The skirts had a lot of wear, and the cylinder walls are polished where the piston was rubbing. There are also some vertical scratches on the cylinder walls, but nothing that catches my fingernail. I also found sand like aluminum grit in the bottom of the oil pan. All the rod bearings look very good, and I had good oil pressure (verified with aftermarket gauge), so I think it was piston skirt material. I will be checking the lower main bearings however.
So not what I was expecting. My next step is I will be checking the cylinders very carefully with a bore gauge and see where I'm at. Hopefully they will all be in spec. I also decided I wasn't going to hone as there is no way to ensure honing grit doesn't get down into the main bearings. Didn't want to risk main bearing damage, and was going to go with a top moly ring which requires a smoother cylinder wall finish anyways. Still don't want to hone with the block in the Jeep, but not liking the polished areas from piston slap, and the factory cross hatching isn't as prominent as I was hoping it would be.
I think this engine had poor maintenance at some point and these issues are from past sludge and loss of proper cylinder wall oiling. My oil never stayed clean long, so I think there was more blowby than I thought despite a very good compression test on all cylinders.
I got it all apart on Saturday. The first thing I noticed was the carbon buildup was very bad in the intake manifold, and top of pistons down into the 1st ring. I also think the head gasket might not be factory, It was a MLS gasket, but it had blue sealing residue around the openings that I don't think is factory, but maybe I'm wrong. Once I got the pistons out I found the piston skirts intact with no visible cracks much to my surprise.
What I did find was evidence of very bad piston slap on all of the cylinders. Surprisingly, the compression (non-power) side of the pistons had more evidence of slap than the thrust side (camshaft side). The skirts had a lot of wear, and the cylinder walls are polished where the piston was rubbing. There are also some vertical scratches on the cylinder walls, but nothing that catches my fingernail. I also found sand like aluminum grit in the bottom of the oil pan. All the rod bearings look very good, and I had good oil pressure (verified with aftermarket gauge), so I think it was piston skirt material. I will be checking the lower main bearings however.
So not what I was expecting. My next step is I will be checking the cylinders very carefully with a bore gauge and see where I'm at. Hopefully they will all be in spec. I also decided I wasn't going to hone as there is no way to ensure honing grit doesn't get down into the main bearings. Didn't want to risk main bearing damage, and was going to go with a top moly ring which requires a smoother cylinder wall finish anyways. Still don't want to hone with the block in the Jeep, but not liking the polished areas from piston slap, and the factory cross hatching isn't as prominent as I was hoping it would be.
I think this engine had poor maintenance at some point and these issues are from past sludge and loss of proper cylinder wall oiling. My oil never stayed clean long, so I think there was more blowby than I thought despite a very good compression test on all cylinders.
