RedJeepster1
Active member
Working on the neighbors Jeep tonight. Took down the oil pan to do the rear main seal. First thing we noticed is it’s missed an oil change or two in its life. Everything is pretty dark. Mildly sludgy but not terrible. Screen on the oil pump was clean and the oil was dark but clean.
So then we start looking in the bottom of the oil pan…. Bearing material… so that’s not ideal. But the bearing material was stuck in a thick sludge at the bottom of the sump. This motor has been replaced. And lots of stuff was loose. So maybe he previous owners were hacks and reused the pan without cleaning it well? Regardless, now we are going to pull every bearing cap and check the bearings, just to be safe. (The motor runs quiet and makes good oil pressure btw)
So one by one we pulled bearing caps, cleaned them, inspected them, oiled them, reinstalled, torqued to spec, and spun the motor over to make sure everything was still happy. All was fine until main bearing cap number 6 (between cylinders 5 and 6). Pulled, looked great, cleaned it up, oiled the bearing, reinstalled. Torqued it down. Motor won’t turn over…. Well shit. Pulled. Reinspected. Spun the motor over with the cap off. Spins fine so we know this is the problem. Confirmed it’s going on the right way. Reinstall and the motor won’t turn over again. So I had the idea. What happens if we install it backwards? The bearings have a tab which indicates which direction they get installed. Well sure as shit we installed it “backwards” from how it’s intended to be and the motor spins over perfectly…
So anyone ever hear of a main bearing cap getting line bored backwards at the factory? With the cap the correct orientation, the motor doesn’t spin over at all. It’s seized up. With it backwards (bearing tabs facing each other) it spins over perfectly. I called my father and he was baffled. But everything I’m seeing is telling me it must have been this way all along. Bearing wear looks great. It bolts right up, it’s just technically not right. But it’s clearly the way it wants to be assembled.
And just for reference this is a 99 Jeep Cherokee 4.0.
Sent from my iPhone using Tapatalk Pro
So then we start looking in the bottom of the oil pan…. Bearing material… so that’s not ideal. But the bearing material was stuck in a thick sludge at the bottom of the sump. This motor has been replaced. And lots of stuff was loose. So maybe he previous owners were hacks and reused the pan without cleaning it well? Regardless, now we are going to pull every bearing cap and check the bearings, just to be safe. (The motor runs quiet and makes good oil pressure btw)
So one by one we pulled bearing caps, cleaned them, inspected them, oiled them, reinstalled, torqued to spec, and spun the motor over to make sure everything was still happy. All was fine until main bearing cap number 6 (between cylinders 5 and 6). Pulled, looked great, cleaned it up, oiled the bearing, reinstalled. Torqued it down. Motor won’t turn over…. Well shit. Pulled. Reinspected. Spun the motor over with the cap off. Spins fine so we know this is the problem. Confirmed it’s going on the right way. Reinstall and the motor won’t turn over again. So I had the idea. What happens if we install it backwards? The bearings have a tab which indicates which direction they get installed. Well sure as shit we installed it “backwards” from how it’s intended to be and the motor spins over perfectly…
So anyone ever hear of a main bearing cap getting line bored backwards at the factory? With the cap the correct orientation, the motor doesn’t spin over at all. It’s seized up. With it backwards (bearing tabs facing each other) it spins over perfectly. I called my father and he was baffled. But everything I’m seeing is telling me it must have been this way all along. Bearing wear looks great. It bolts right up, it’s just technically not right. But it’s clearly the way it wants to be assembled.
And just for reference this is a 99 Jeep Cherokee 4.0.
Sent from my iPhone using Tapatalk Pro
