I have a tired 1993 Grand Cherokee with a 5.2L V8 (ZJ?). It's oil pressure is good when the engine is cold but it drops to near zero when hot. The engine sounds good when it is first started (Cold). When the engine is hot there is a knock that sounds like a main bearing. Had a mechanic check the oil pressure to verify gauge readings and he confirmed the pressure drop and believes the main bearings are gone. He wants $2000+ to pull the engine and replace the mains and oil pump. I want to squeeze a few more miles out of her and I don't think it is worth pulling the engine and reworking the crankshaft etc. Can the main bearings be replaced without removing the engine? I know it's possible with the inline 6 cyl but is it possible for the V8?
This is just a play vehicle now since I've had it for 15 years.
Remove the oil pan and the bearing caps. You can tap the top half of the bearing out with a small wooden dowel until it spins enough to where the end sticks out. You can then gingerly use a punch to move it along the circumference of the crank. If you remove the timing chain (PITA), the frontmost top bearing half moves way easier. Chrysler makes a special tool for this onerous chore, but my dealer wouldn't sell me one.
the bearings are usually marked for size, if it has worn off of the stockers, it will be located on the last counterweight on the crank. it's in code, don't remember the specifics, should be able to find it online.
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.
Starting to look possible to me (and I haven't had any beer). It would be a big waste of effort if my crank is badly scored... but since it runs pretty well when it's cold, just maybe the crank isn't too bad. The compression is good so the upper end is fairly solid.