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Slow Oil Leak

Q

Quailman

NAXJA Forum User
Location
Hunt Valley, MD
Hi all,
I'm having a slow oil leak coming from the very front of my oil pan where it meets the bell housing in my 96 xj sport.
I'm well aware that slow fluid leaks are inevitable in a 21 year old vehicle, and I'm not overly concerned about it (as my oil level doesn't seem to be dropping, I've been checking it frequently). I will probably replace the oil pan gasket as well as the rear main seal the next time I change my oil just for good measure.

I am honestly trying to satisfy my own curiosity more than anything. The oil doesn't seem to leak while the jeep is running, and also doesn't continue to leak while sitting. It ONLY seems to leak when I initially shut the jeep off (5-6 drops) which I thought was a bit strange.
Has anyone else experienced this before?

Thanks in advance,
John
 
Quailman said:
Hi all,
I'm having a slow oil leak coming from the very front of my oil pan where it meets the bell housing in my 96 xj sport.
I'm well aware that slow fluid leaks are inevitable in a 21 year old vehicle, and I'm not overly concerned about it (as my oil level doesn't seem to be dropping, I've been checking it frequently). I will probably replace the oil pan gasket as well as the rear main seal the next time I change my oil just for good measure.

I am honestly trying to satisfy my own curiosity more than anything. The oil doesn't seem to leak while the jeep is running, and also doesn't continue to leak while sitting. It ONLY seems to leak when I initially shut the jeep off (5-6 drops) which I thought was a bit strange.
Has anyone else experienced this before?

Thanks in advance,
John
Click to expand...

A drip from the front main seal is fairly common issue. I've done a few of those myself. Get a longer bolt and an extra nut to reinstall the harmonic balancer. If you try to pull the HD on with the stock-length bolt, you'll rip the first couple of threads out of the end of the crank. Thread the longer bolt in until it bottoms out and then use the nut on the bolt to push the HD on instead. Install and torque the stock bolt once the HD is close to being seated.

The rear main is much more involved and messy, so I wouldn't tackle that unless you're sure it's leaking. Depending on how much lift you have, it can be difficult to get the oil pan out.
 
lawsoncl said:
A drip from the front main seal is fairly common issue. I've done a few of those myself. Get a longer bolt and an extra nut to reinstall the harmonic balancer. If you try to pull the HD on with the stock-length bolt, you'll rip the first couple of threads out of the end of the crank. Thread the longer bolt in until it bottoms out and then use the nut on the bolt to push the HD on instead. Install and torque the stock bolt once the HD is close to being seated.

The rear main is much more involved and messy, so I wouldn't tackle that unless you're sure it's leaking. Depending on how much lift you have, it can be difficult to get the oil pan out.
Click to expand...

Hmm. I'm not sure that the leak is coming from the front main seal. I'll take another look to double check again but it looks to me like the leak is coming from the very front of the actual oil pan.
 
The front main seal is the one that goes around the crankshaft that the harmonic balancer fits through.
 
old_man said:
The front main seal is the one that goes around the crankshaft that the harmonic balancer fits through.
Click to expand...

I can't find anything for "front main seal" on rockauto or napa or anywhere.
The only thing I can find is "timing cover seal" which I think is the same thing but I'm not sure.
 
Lots of mixed up terminology in this thread. :dunno:

The bell housing is in the back where the transmission bolts to the motor.

The rear main seal is where the crank exits the block towards the transmission.

The harmonic balancer is pressed onto the crank. There is a seal in the timing cover that rides along the harmonic balancer. This seal is commonly referred to as the front crank seal.

It's possible that the oil pan gasket itself is leaking at the front of the pan. Or it could be coming down from the front crank seal. Or both.

Sometimes the oil pan boils become loose and need to be snugged up.

If you are going to replace the oil pan gasket, RMS, and front crank seal, buy the Fel Pro Combination Gasket Set. You get all the seals and gaskets you'll need and its about the same cost as the oil pan gasket itself.
 
Last edited:
First thing you need to do is clean the motor so you can identify where the oil is coming from !!!
 
I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.
 
Okay everyone, so upon closer inspection it may be a coolant leak from the upper radiator hose.
The fluid leaking doesn't LOOK like coolant (to me, but what do I know), however there's some gunk around the base of my upper radiator hose. If that's what it is, it's at a perfect angle to drip right down to where the front crank seal is, disguising itself as an oil leak.
This would also explain why my engine runs on the hot end.
Thoughts?
 
md21722 said:
This. Replace the fan clutch. Radiator caps should hold 16 psi, if they don't, coolant boils at a lower temperature.
Click to expand...

Replacing upper rad hose (pretty sure that's where the leak is coming from) also the tstat while Im in there and the rad cap. If it still runs hot I'll swap the clutch. Thanks guys
 
Did all that and it's definitely running cooler! Also confirmed that the upper rad hose is where the leak was coming from.
Also, the fact that I had to fill way more coolant into the Reservoir than what leaked out tells me that maybe there's been air bubbles in there for a while and that's why it was running hot? Just needed a good burpin?
 
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