so in the morning I am replacing my rear main seal

[jeep-N-montero]

On Friday I was coming down I-15 from about 20 miles north of here and I look in the mirrors to see smoke coming out the back. I immediately pull over to check things out and discover the smoke was caused by oil dripping onto the exhaust from between the engine and tranny. Added some oil and drove it home, oil has a high flashpoint so I wasn't to worried. Picked up the new seal and oil pan gasket yesterday and will get going on it in the morning, seems pretty easy though, just a bit timely. I found several good write-ups online including this one if anyone else is looking http://jeep-xj.info/HowtoRearMain.htm

Wish me luck!!

 

[Bigjerm]

The rear main is leaking on my 06 LJ with a little less than 21k miles :Wow1: Pretty I bought a warranty when I bought it so hopefully someone else gets to do the dirty work with no charge to me.

 

[jeep-N-montero]

So after closer inspection it is ATF dripping down, off to the shop it goes!

 

[BigAl]

I have done several rear main seals on 4.0s, the job is not hard, but my success rate sucks. Most of them still drip slightly?

 

[meatblanket]

I have done several rear main seals on 4.0s, the job is not hard, but my success rate sucks. Most of them still drip slightly?

It's probably not your fault. Sometimes with a well worn engine, you get enough crankcase pressure due to blowby that it will push oil past even a new seal.

 

[Doctor W]

It's probably not your fault. Sometimes with a well worn engine, you get enough crankcase pressure due to blowby that it will push oil past even a new seal.

That's because the PCV, or in the case of 4.0 Jeeps the CCV system is all clogged up and pressurises the crankcase, resulting in leaks.

Best fix is to replace the CCV orifice and breather and their grommets on top of the rocker cover (cost is about $25) and then....at every oil change before dumping the old oil spray aerosol Carby Cleaner into the CCV orifice and breather by diconnecting their respective hoses.....then dump the now fully contaminated oil.

 

[taggart_lumpy]

this is on my list of thing to do as well

 

[meatblanket]

That's a good suggestion, if your CCV is clogged, then you will experience high crankcase pressures. The factory CCV is borderline inadequate to begin with, so it needs to be clean.

However, with a worn engine you can develop crankcase pressure well over what even a clean CCV can deal with.

 

[Bigjerm]

Well mine goes to the dealer Monday. I got 3 yrs / 36k from when I bought it so might as well use it, right? So far I am a little less than a yr and 6k into it.

 

[jeep-N-montero]

Well mine goes to the dealer Monday. I got 3 yrs / 36k from when I bought it so might as well use it, right? So far I am a little less than a yr and 6k into it.

To be honest I would just do it myself, it's only $40 in parts and 2-3 hours of your time. You get the assurance it was done right and you don't have to leave it with the stealership all week being worried if your rig will be the same when you pick it up. Warranty work is last on their list because it is last to get billed out.

 

[Bigjerm]

Naw they said it would be ready in a few hours and again its free so can't beat it. Sounds like this is a pretty common issue with the 4.0 so I will keep going to the dealer till it isnt free and then deal with it my self.

 

[macgyver_ga]

Just a thought here from my previous life wrenching on turbo cars...

Has anyone ever thought about running an oil catch can and removing the PCV/CCV entirely? Obviously you will have to drain the catch can periodically but that's not that big of a deal. This would remove the possibility of the PCV/CCV getting clogged up and keep the crankcase at atmospheric pressure.

 

[dstock]

Couple other things to consider...

One, make sure oil does not get overfilled (esp when at dealer), sure way to make a mess of your main seal.

Two, get a one piece gasket for the oil pan, most of the aftermarket jeep places sell these. The OEM gasket is a 3 piece design and leaks accordingly.

I replaced a couple of main seals and the oil pan gaskets and nary a drip to fall after.

Another common leakage point is the oil filter adapter where it attaches to the block, these tend to get leaky over the years as well.

Good luck!

 

[jeep-N-montero]

Ended up being a pinhole in the tq converter.

 

[Bigjerm]

Well never did take mine to the dealer... turns out there is a $100 deductible on the warranty policy. Not bad for a big job but I won't pay a $100 for a rear main on the LJ. I have not notice it drip lately though after a cleaning/degrease of the area.