ERock 2010

I have a 95 jeep grand cherokee 5.2 v8 4x4.it has its normal problems as most jeeps do... My main problem for now...I have a oil leak....was told by the guy I bought it from..that its leaking from the rear main seal... well I plan on changeing this as soon as i get a np 231 and doping it all at one time....well my question is after I top off the oil...while cold...I start jeep ley it warm up oil ptessure is.at 60 psi ...after driving for 10 minutes its down to 40 psi....and after 30 minutes its down to 20 psi and it idles real low and kinda has a Miss to it....stop turn the jeep off check oil and its full...ley cool down and it still says full....????? With the rear main leaking will this cause oil pressure to decresse this progressively?????

dave1123

Make sure you're not getting gas in your oil. That would thin it down yet evaporate on cooldown. The worst case I've seen was you could light the stick with a cigarette lighter!

Just my opinion.

ERock 2010

Ok ill try that....it never smelt like gas......

ERock 2010

I checked it again still reading full....and didnt smell any gas.....tries to lite on fire didnt catch fire....so as far as i can tell no gas in the oil.....by the way what would cause gas to get in the oil? I guess through the valves?

ERock 2010

Or should I try that theory when motor is warm.?

dave1123

A lightning bolt just hit me! Maybe your oil pressure sensor is at fault. Is it leaking? Sometimes a leaking sensor will run down the edge of the pan and drip off the rear and look like a rear seal leak. On the older 4.0s, it was not uncommon to whack it with a wrench when changing the oil filter.

ERock 2010

Oh and the leal is bad enough that I have to put a quart of oil in every time i filo up......:

ERock 2010

Is it located on the back of the block or on the side?

dave1123

Not sure on the V8s. It should be near the oil filter.

ERock 2010

I guess it is possible that both the rear main seal and oil sensor are leaking.....

ERock 2010

I found it....on passenger side mear the distribitor......I cant ser it bit I can feel it....

mxpxpunkrock1987

well usually the intake gaskets leak causing the leak thew gakets were never changed i had to for mine and had to remove valve cover to clean return valleys and then ran full trans fluid through engine to wash out everything then change oil and filter and pressure sensor all runs good now i'm at 228,000 plus all original except fan clutch alt and ac compressor and pullys

ERock 2010

Yeah this motor is right at 200,000 very clean a well maintained . But stuff is starting to show wear.....im using as a daily driver untill I get home to nc...im in new Orleans now ....thats a 15 hr ride.in just gonna jeep the oil topped off and rey to make it home for christmas......

jasper

I just joined the forum and I think you might be the perfect people to ask this. I gave my friend a 4.0L 96 Cherokee when I got my new car. He changed the oil and filter put about 5.5 quarts in it and after a quick drive it all started pouring out and he described what sounds to my like the oil pressure sensor right next to the filter. It was taped together when I got it and never worked but I never bothered to change it. Is it possible that a serious amount of oil could come out of here if it broke?

dave1123

A Serious Amount of oil! Straight off the pump! 40 psi with full flow. You'll have to put a pipe plug in it to drive it to the auto parts store.

The 4.0s oil pressure sensor is very often whacked with an oil filter wrench. A common mistake for a novice mechanic.