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Rear main

T

trust96xj

NAXJA Forum User
Location
redlands
Woke up this morning to a drop of oil underneath my truck. I gasped a little, then went to work. On my lunch break I lifted the truck up to take a gander. Rear main is leaking ever so slightly. Only leaked after a decent length drive. How long can I put off doing this? A drop here and there will annoy but not kill me. How long will this last till it goes? Will it just go and leak everywhere? Never dealt with this before. Thanks for any answers guys.
 
Mine has been leaking for about 50K. It's not bad since I don't have to add any oil between changes, but I really should do it.

JIM.
 
Yea i figured if need a hoist at least and I don't have one anymore so I calle a couple shops. Most said ~$800!! What the hell! I'll do it myself. I'll monitor and see how much I lose. If its a drop a day I'm not going to mind it. Thanks go the input guys. Appreciate it!
 
My crossover pipe behind the pan is black and you can see smoke roll from under it, but I only lose about a qt every oil change.

mini stroker time...
 
*89Laredo* said:
My crossover pipe behind the pan is black and you can see smoke roll from under it, but I only lose about a qt every oil change.

mini stroker time...
Click to expand...

Mine was like that also, that cross over pipe was just blackened and I would get rather large puffs of smoke from behind the XJ on steep hills. I presume the oil was being pushed out suddenly and hitting the cross over. Since doing the RMS the cross over pipe is back to being just rusty and no signs of being blackened. :flame:
 
A 4.0 Jeep RMS leaking is like a badge of courage, sort of like the US Army Combat Infantryman Badge. If you don't have an RMS leak you ain't chit. :roll:

I had leak for a long time. I started to use Valvoline 10W-30 Max Life and that slowed it down considerably. Just got so bad, leakng on my $3,000 driveway, I had to change it. I just took the pain and did it myself. One dealer quoted me $950 to do it and another, $650. Madness!
 
Mine's been seeping since I bought it in 06 with 99,000 on it. It's at 166,000 now.
I too switched to Valvoline 10w30 MaxLife syn blend, and it slowed down considerably. Just enough to need a wipedown every oil change. One paper towel and the pan is shiny black again.
I keep the seal and tools required in the Jeep JIC a catastrophic failure occurs.
 
I'd be looking up above first, and VERIFYING the source of the oil leak yourself. Many mechanics, friends, and good old Uncle Bob love to tell 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, you’re good to go on your own. Don't jump on the RMS/oil pan gasket bandwagon just yet.

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. "$hit 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.
Revised 8-15-2012
 
One thing many of us forget to check is the CCV line and orifice to see if it is breathing properly. If not, the exhaust gasses can build pressure in the crankcase and push oil out the rear seal, instead of having a mild vacuum on the inside holding oil in.
 
so after half a year of rms leaks I went to tackle it. I could not get the top half out!!! I took some pressure off the nuts next to it to maybe help release it but no luck. I did not want to scratch any surfaces so I called it a night. Any suggestions on pushing out a stuck rms?
 
Spray it with PB Blaster several times, and soak in between for several hours.

I would not call Uncle Bob for help or use BFH.
 
slowjeep said:
spray PB Blaster on the top half?
Click to expand...

Yes, spray it on the edges of the seal to engine metal joints. It is an aerosol, penetrating lubricant, rust, and dried gunk loosener.
 
slowjeep said:
so after half a year of rms leaks I went to tackle it. I could not get the top half out!!! I took some pressure off the nuts next to it to maybe help release it but no luck. I did not want to scratch any surfaces so I called it a night. Any suggestions on pushing out a stuck rms?
Click to expand...

If you haven't done so already, remove the girdle.

Next, loosen all the bearing cap bolts a bit (but don't remove them) and loosen the lower bearing caps to take pressure off the crankshaft.

Now, try tapping out the top RMS. I used a small piece of brass rod, ground down to match the seal head, as mine was stubborn too. Loosening the bearing caps really helped...
 
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