Help, What is the Most Common Source of Oil Leak

Okay so I was pulling the XJ out of my garage today and I noticed a fresh oil spot on the floor. There was never a spot before, and before everyone replies telling me I am very lucky not to have any leaks until now or that all Cherokees and 4.0Ls leak, I would really like to get some thoughts about what might be causing the leak and where it is most likely coming from.

The leak is in fact motor oil. When I looked under the Jeep it looks like it may
be coming from between the engine and transmission but the engine oil pan and transmission pan are both moist with oil as well,but I figure the oil on the transmission pan could just be from air pressure blowing drips back during driving.

My Jeep only has 60K miles and I never noticed a leak before so I am wondering what could be causing it and where could it be coming from?

I have noticed lately that my oil pressure gauge shoots skyward and pins itself all the way on 80 at some cold starts but if I turn off the ignition and turn it back on it goes back to normal, so I think this is a gauge issue not a mechanical issue. Any thoughts on this?

Also it has been really cold here in Delaware the last few weeks and I have been using my remote start in the morning and before I leave work almost everyday. Could extended idling 10-15 minutes twice a day be causing this leak or making it worse.

Could my oil gauge issue or warm up habits be causing the leak? If so how? And if it is just random what is the most likely source of the leak so I know what kind of repair to make?

I appreciate any guidance or thoughts.

Thanks,
Steve

Sounds like a rear main seal to me... The gauge issue is probably related to the sending unit (Found on the oil filter housing).

Your warm up habits are good, you never want to take off driving with a cold motor, that's when you CAN build excess oil pressure, due to the oil being extra thick, and that'll cause you to actually push a seal out... But i'm doubting that's what happend in your case.

Go ahead and replace that rear main, and i'd also do the oil pan gasket while you are there.

Another possibility could be a leak from the rear of the valve cover, stick your hand back there and feel around.

All are simple procedures, and if you have any wrenching abilities at all, you shouldn't have a problem.

Sounds like a rear main seal to me. Do a search, theres a ton of write-ups. If your at all mechanically inclined and have a basic selection of tools you can do the job in an afternoon yourself. Plan on a little more time if it's the first time youve removed the oil pan as it can be a bit of a pain to get off. The most time consuming part for me was removing the oil pan and scraping old gasket off the block/using a wire wheel and parts cleaner to get the oil pan all clean. Putting in the new seal took no more than 20 minutes, but in total the job took a LONG time because the oil pan was a real pain. I wrote a post with a few tips not long ago, it'll probably come up in the search.

Oh, and you are probably noticing the leak more now because it's idling in one spot for 10-15 minutes. Mine wouldn't start really leaking until it was all warmed up, then it would let loose. Yours has probably been leaking for a while, you just havn't noticed it until now.

Okay I was thinking rear main seal as well but I wasn't sure. I am a pretty competent mechanic so if you say it is easy that is a relief, i can probably handle it.

I am at work right now so I can't look, but is replacing the rear main seal something the Haynes manual will cover sufficiently or does anyone have a link to a good writeup? I swear I saw a good one once but it seems I failed to bookmark it.

Any pointers or things to keep in mind with this procedure?

Thanks,
Steve

before you start planning a RMS job, feel around the back of the valve cover for leaks. Because the engine slants back, oil constantly sits around the back of the valve cover--when the gasket goes it'll leak like hell and run down the back of the engine, and look exactly like a leaky RMS.

Also, the oil filter adapter is known to leak. Theres a small o-ring in there.

Do a search on these two topics and read up before you diagnose the problem completely.

I think you are right about it leaking for a while and only noticing it now. There has always been a little oil around there when doing oil changes but my guess is, as you said the recent idling is allowing it to gather a bit more, making it noticeable.

http://www.jeepin.com/features/rearmain/

http://www.go.jeep-xj.info/HowtoRearMain.htm

theres two to get you started. I'd really suggest doing a search and doing some reading when you get home too, theres alot of little tips that will make the job easier.
My haynes manual has the procedure in there, although I found that a combination of the haynes manual and some tech write-ups from online made it easy. Just be sure to tighten the bearing cap bolts back to spec!!(85ft lbs). Some people seem to get excited, forget to torque the bolt to it's final stage and throw everything back together, only to drive down the street and spin a bearing a few minutes later..

Good advice, I have been running a T-case drop too so it may very well be the valve cover. As for the filter housing "O" ring. Do I just remove the filter to get to this? And is this an O-ring you order by name or part number or do you just match one up?

What kind of seals are you guys using? Jeep or aftermarket, any arguement for one or the other?

92westshady said:

Good advice, I have been running a T-case drop too so it may very well be the valve cover. As for the filter housing "O" ring. Do I just remove the filter to get to this? And is this an O-ring you order by name or part number or do you just match one up?

Click to expand...

hit www.madxj.com for a very good writeup about the oil filter adapter.
You'll need to take off the 90* adapter, and it's three o rings, they're available at the dealer, cost you about $5.

For the oil filter adapter go-jeep posted a pretty good write-up

http://www.go.jeep-xj.info/HowtoOilAdaptorOrings.htm

The o-rings you can get at the dealer. They are about $10 and they should have them in stock.

Tim

http://www.naxja.org/forum/showthread.php?t=101118
5-90 wrote up a good rear main replacement article as well... worked for me!

dutchjeep said:

For the oil filter adapter go-jeep posted a pretty good write-up

http://www.go.jeep-xj.info/HowtoOilAdaptorOrings.htm

The o-rings you can get at the dealer. They are about $10 and they should have them in stock.

Tim

Click to expand...

The o-rings SET from the dealer was about $4 or so when I got some last month.

Make sure you get the SET. They sell just the o-ring you need, but there are two others that you should go ahead and replace while you have everything out.

I followed this write up with good results. http://www.yuccaman.com/jeep/filter.html

You're going to have to be creative as to how you're going to get the bolt out of the adaptor, as there is not enough room to clear the T60 torx bit, as well as a socket wrench.

Man, my dealer is a stealer! Anyway, those rings shouldn't cost a buck in the first place!

Just to toss some more info on you, there is also a discussion on the adaptor housing bolt @

http://www.naxja.org/forum/showthread.php?t=904592

This is great guys. Thanks for all the links, i am bookmarking them all in my Jeep Information folder. I've got enough info to do all the jobs now but I guess I will check out the filter housing and valve cover for leaks first these seem less involved than the rear main seal.

So I did a little investigation at lunch. It seems that the valve cover gasket is fine, the back of the block is dry. There is what I would call signs of oil and grim on the left side of the block but it doesn't look real bad around the oil filter housing.

What is strange is that there is wet oil around the oil sending unit and since the oil pressure has been pegging on 80 lately I wonder if it is feasible that my the eak is coming fromt he sending unit?

Is there any harm in pouring some dye in the engine oil to try and source the leak with a black light? I guess there is the fact that the dye and black light bulb will be more expensive than set of O-rings for the filter housing and half the price of a new sending unit.

What do you guys think?

it's is certainly possible that the sending unit is the leak.
especially if it was damaged/tweaked during an oil cahnge.

87manche said:

it's is certainly possible that the sending unit is the leak.
especially if it was damaged/tweaked during an oil cahnge.

Click to expand...

X2. It's very easy to hit that thing when changing the oil, and it wouldn't be the first case i've seen on here of it.

Well I am due for an oil change and some other maintenance this weekend so I figure I will replace the sending unit and filter housing o-rings while I am at it and see where that gets me.

If its still leaking ... I'll know it is on to the rear main seal.

Steve, DO make sure you check the oil filter adapter for leaks (and the seal kit has 3 'o' rings in it)
I 'put off' my rear main seal job for about 3 years and then thought I would do the easier filter leak first and now have NO leaks at he rear of the engine at all, am I happy! Pretty simple job but you need a big (T60 I think) torx bit that is short enough to fit inside the frame (chassis?) rail.I had to press the torx bit out of the 1/2" drive socket it came in and use a ring spanner on the end of the torx bit to get the clearance.
Regards, Paul
'94 XJ sports (stock)