FRN

I have a 1998 cherokee limited with 74k original miles on a 4.oL engine. Since I have owned this Jeep, I put Mobil 1 in it at 67k. Now I have a significant rear main seal leak, and when it is warm, the oil pressure drops to 10- psi. When driving the pressure is 40 psi. I am told I could need a oil pump, main bearing etc..
Anyone else have suggestions as to what it might be? I am sick over this. My parents were the original owners, always took great care of the vehicle, was told by many that the engine is bullet proof, that I should get 200k+ from engine. Then this happens!

Cherockee

Before you get too excited, check around you oil pressure sender. When they leak it can look just like a RMS leak because the oil will run around the pan until it gets to that area. The sender could be the cause of the low reading

RTorrez1

First thing you need to do is verify the oil pressure with a mechanical oil pressure gauge. Also what brand of oil filter did you put on at the last oil change?

FRN

Thanks for the replies,
I used a fram xtra guard.

RTorrez1

Get rid of the fram filter they are garbage! Pick up a Wix or Mopar brand that may help it some too.

jebmccall

frams have been known for several issues especially on the 4.0, causing low oil psi, and coming apart. they are known as an orange can of death. i run wix,mopar,and napa gold only on my jeep. after changing the filter verify the oil pressure with a mechanical gauge.

FRN

after talking it over with my mechanic, he also thinks it is the oil sending unit. I crawled under it yesterday, and I noticed oil dripping from up around the oil filter, then it looked like it made its way back via the pan to the RMS area. So I ordered a new sending unit, and take it from there.
Thanks again for all the replies!

Kalali

Also, do a thorough degreasing of all the dirty areas. And if it were my Jeep, I would use regular non-synthetic oil. I know some will disagree but there is no benefit in using synthetic oil if you change the oil/filter every 5K miles. At 75K the motor is just breaking in. Take good care of it and the engine will be your last problem with the rig.

soundrew

Kalali, you could change petroleum oil every 3 days and it wouldn't raise the film strength (ability of oil to stay between moving parts) or lower the pour point (ability to stay fluid at low temperatures).