89 MJ oil leak where the motor meets the tranny

[StuMesa]

Hey gents,

just bought an 89 MJ 4x4 stick with the 4.0, and have noticed a slight leak of oil coming from right where the motor meets the transmission, I haven't had a whole lot of time to look at it and make sure its not dripping down from somewhere else but ill do that today, any thoughts on what it could be or something I can use to fix it?

Thanks in advance!

Stu

[Blue XJ]

Its probably the rear main. Its not a hard job to replace, but it's very time consuming.

[87MJTIM]

Before you go and replace the RMS, check other places first for oil leaks first.  Check the back of the valve cover.  Check the oil pressure sender.  Check where the dizzy goes into the block.  You may need to clean the engine off, run it for several minutes and check for leaks in these places.  

 

Remember, oil will run down to the lowest spot.  This is where the oil pan and trans bell housing are.  The 4.0 tilts up in the front, so all the oil will collect in the rear.

 

If you eliminate these other locations, then get a FelPro rubber oil pan gasket and RMS.  If you will do it yourself, plan for several DIRTY hours.  It not too hard, just dirty.

[StuMesa]

Thanks! ill check it out tomorrow and see whats up.

[Heavy Metal]

My oil filter adapter was leaking a small amount of oil, and it would collect on the rear or my oil pan near the drain plug and the bottom of the bell housing as well. There are three o-rings in the adapter. 

[cruiser54]

Before you go and replace the RMS, check other places first for oil leaks first.  Check the back of the valve cover.  Check the oil pressure sender.  Check where the dizzy goes into the block.  You may need to clean the engine off, run it for several minutes and check for leaks in these places.  

 

Remember, oil will run down to the lowest spot.  This is where the oil pan and trans bell housing are.  The 4.0 tilts up in the front, so all the oil will collect in the rear.

 

If you eliminate these other locations, then get a FelPro rubber oil pan gasket and RMS.  If you will do it yourself, plan for several DIRTY hours.  It not too hard, just dirty.

Like this?

 

 

 

 

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, people on Jeep forums who can’t see your Jeep from where they’re at, 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. "$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 02-26-2013