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Another Rear Main Seal Topic


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I've had a pretty good oil leak since I bought the truck. It only leaks when the trucks running though. So I cleaned the engine as much as I could with my trusty garden hose. Then cranked the engine and left itrunning a bit. Came back with a flashlight and went to searching. It does seem to be running from the RMS place. I was just wondering if the RMS only leaks when the engine is running, if not then what would seem like a RMS leak but wasn't? Also how much would a shop averagely charge to change it out and how hard would it be to do it myself?

 

Thanks.

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The rear main on my old '86 leaked all the time but was very bad when running, so bad that there was a trail of oil leading up to the stop sign on the street my gf lived on. I took it to a shop and was told $1800 to $2200 I think, guy said the engine would have to be pulled. I tried to fight with him on it because I knew from looking around the internet that it could be done by dropping the tranny instead. Either way not a fun job I'm sure, so if you are able to I would do it yourself. I ended up selling mine rather than deal with it any longer, but I had a weak 2.8L so it wasn't as hard to part with as a good running 4.0L.

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I know for sure that a 4.0 RMS can be changed by dropping the oil pan instead of removing the tranny. the 2.5 has to have the tranny dropped, I believe. I don't know about the 2.8. If a shop was to charge that much then Id deff do it myself.

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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
 

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The RMS on my XJ is what got me started on this crazy journey.  They told me the part was $15.00 and the labor was $650.00.  I could not live with that, so I got a manual, got on a Jeep forum and asked how it's done.  I had only minimally worked on any vehicle before that 10 yrs ago.  I spent a whole day doing it...but it was worth it...I don't make $650 a day.  Time to get dirty.

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I ignored the leak on my 4.0 MJ for two years, finally got so bad I was losing a quart of oil over a month of street driving, or one day of hard wheeling. Turned out of be the RMS.

 

Don't know what engine you have, but on a 4.0 it can be done without removing the engine or transmission. You do need to remove the oil pan, and you will need a RMS (obviously), oil pan gasket, and a tube of anaerobic RTV (Loctite 518, difficult to find in parts stores, but Summit Racing has it available through mail order).

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10W30. I use either Quaker State Defy, or Mobil 1 high mileage. Both of those are still API SL. Despite what the oil companies say, API SM and SN are NOT backwards compatible.

 

4 cycle motorcycle oils are still API SJ because even SL doesn't have enough zddp for those engines, but it is usually only available as 10W40 or 15W40.

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