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Unread 09-30-2013, 07:54 PM   #1
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Join Date: Jun 2011
Location: san diego, ca
Posts: 16
Leaky rear main seal and engine overhaul questions

So I've got a leaky rear main seal, which I believe could be caused by the fact that my bearings are worn and I have a lifter tick. Question is if I put in a new seal do you think my wobbly engine will just tear it up quickly? And in that case should I just do bearings and seals in one go.

Also my compression is definitely not what it used to be, I was thinking about checking out my pistons and maybe putting new rings on them. Would you always have to re-hone the cylinders and put in larger pistons for this purpose or can you get away with just rings?

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Unread 10-01-2013, 02:48 PM   #2
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1996 XJ Cherokee 
Join Date: Feb 2010
Location: Gurnee
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If loose-ness in the engine caused the seal to fail, then it will knock out the new seal fairly quick. But if the bearings were loose enough to cause that, your oil pressure should be low and youd probably have engine noise most likely coming from the bottom end, not from the lifters. Have you checked your oil pressure with a mechanical gauge?

Just to change the rings, yes to cylinder honing, no to larger pistons. Only reason to put in larger pistons is if the cylinders are out of round, have a significant amount of taper due to wear, or if there is damage to the cylinder walls or pistons. In that case the cylinders need to be bored out. Before you go and tear the motor down, figure out why its low on compression. What are the compression readings for each cylinder? And how did you do the test? Throttle wide open or closed while cranking? Also, if you suspect bad rings, do a dry compression test, then a wet compression test. If the compression increases by more than 20% with a wet test as opposed to a dry test, that would indicate bad rings. With a leakdown test, air coming through the crank case=bad rings or piston, Throttle body opening=intake valves, exhaust tail pipe=exhaust valves, bubbles coming from radiator filler cap=head gasket.
1996 Jeep Cherokee- Project-- Rusty's 8in long arm, SYE kit, Teraflex driveshaft, Cragar soft 8's 15x10 with 33x12.5 Firestone Destination MT's, Eaton Tru Trac in the front
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