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is it possible to BLOW a rear main (leaking 4.0)


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87 4.0 auto.

 

it's leaking...literally just began leaking today.

 

and pretty badly too. the leaks are dripping from below the oil drain (it's tight and not leaking, but it is the lowest spot on the pan and it's pooling there to drip), and coming out of the CPS hole to leak down on to the driveshaft and down pipe.

 

um...i think it's my dumb butt's fault too....i removed the pcv system to the air box and plugged the hole there :oops: and just now remembered that i need a small filter there :eek: :roll: so as not to build crank-case pressure.

 

so...i'll be putting the filter on, but what are the chances on the rear main still being good?

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About zero.

 

Sorry. It can happen even with a functional vent. I rebuilt a 4.0L XJ for my ex-GF a couple of years ago. Engine had 165,000 miles on it, but ran well after the previous owner's disasters had been straightened out.

 

Once I had everything straightened out, I had to deliver it to her ... in Montana. I made it halfway across PA on I-80 before the rear main seal packed it in. Started spewing oil out. By the time I got to a Wal-Mart about an hour from the Ohio border the oil was down about 3 quarts and the chassis was never going to rust again. I bought a case of house-brand oil and kept going. It was the proverbial "Check the gas and fill up the oil" from there on.

 

Once I got it to Montana, we had her mechanic replace the seal and it was good to go from then on.

 

The good news is that on a 4.0L you can replace the seal without pulling the tranny.

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About zero.

 

Sorry. It can happen even with a functional vent. I rebuilt a 4.0L XJ for my ex-GF a couple of years ago. Engine had 165,000 miles on it, but ran well after the previous owner's disasters had been straightened out.

 

Once I had everything straightened out, I had to deliver it to her ... in Montana. I made it halfway across PA on I-80 before the rear main seal packed it in. Started spewing oil out. By the time I got to a Wal-Mart about an hour from the Ohio border the oil was down about 3 quarts and the chassis was never going to rust again. I bought a case of house-brand oil and kept going. It was the proverbial "Check the gas and fill up the oil" from there on.

 

Once I got it to Montana, we had her mechanic replace the seal and it was good to go from then on.

 

The good news is that on a 4.0L you can replace the seal without pulling the tranny.

 

shucks. oh well.

 

the bad news...i have to drive it for a week like this, making an hour and a half commute per day. oh well, i hope i don't get a fire...

 

on the up-side, the vent is installed...

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Mine was leaking exactly like you described. I thought i had a RMS leak but it turned out to be the valve cover gasket leaking down the back of the engine, down the oil pan past the drain plug and flying back onto the exhaust. The crank pressure probally messed up the valve cover gasket.

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Mine was leaking exactly like you described. I thought i had a RMS leak but it turned out to be the valve cover gasket leaking down the back of the engine, down the oil pan past the drain plug and flying back onto the exhaust. The crank pressure probally messed up the valve cover gasket.

 

unfortunately, that's not the case here...i can see it's dispersal from the CPS hole, and below the top of the bellhousing. even felt behind the cover for wetness...but nothing other than 21 years worth of grime.

 

putting the crankcase filter on the valve cover helped. it's kinda rigged (i think it is at least), but it will work for my purposes. when i put the canister filter in, i will reconnect the PCV system with replacement parts.

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On mine, when i looked up in front of the oil pan I could see the crank spinning and the oil was pooling there before it dripped and ran down the dust shield or whateverit is (thin sheet of metal on front of bell housing). I thought for sure it was the RMS. Atleast you don't have to drop the tranny.

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What does Renix have to do with it? You have a 20 year old engine, probably with the original rear mail seal, so it's all dried out and cracked, and then you disabled the crankcase ventilation system. None of that has anything to do with "Renix." The Renix system was ignition and injection. Rear main seal and crankcase pressure is fundamental power mechanics.

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What does Renix have to do with it? You have a 20 year old engine, probably with the original rear mail seal, so it's all dried out and cracked, and then you disabled the crankcase ventilation system. None of that has anything to do with "Renix." The Renix system was ignition and injection. Rear main seal and crankcase pressure is fundamental power mechanics.

 

restatement;

 

i hate 20 year old 4.0's

 

looking at a HO upgrade...even the EGR valve on this thing apparently isn't working right..

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My rear main always leaked a little since I bought the 88. Then one day it spewed 5 quarts out in the span of about a half hour. :roll:

 

:P

 

sucker seems fine...leaks a few drops, gets a little wet underneath but nothing to cry about.

 

still, i'll be replacing the rear main in the near future.

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My time has come also to replace that curious little RMS 8)

 

Any clues as to remove such oil pan with less of a brain tease effort?

 

Peace ;)

 

yup. ...the front of my truck is lifted 6.5"...sooooo it will be simple as draining fluids, unbolting the pan and rear main cap, pushing out the old rear main, and installing the new one.

 

i'll do the valve cover at the same time so I can flush the motor down with seafoam...will do this before i remove the oil pan, so that it doesn't just drain all over my face...

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My time has come also to replace that curious little RMS 8)

 

Any clues as to remove such oil pan with less of a brain tease effort?

 

Peace ;)

 

yup. ...the front of my truck is lifted 6.5"...sooooo it will be simple as draining fluids, unbolting the pan and rear main cap, pushing out the old rear main, and installing the new one.

 

i'll do the valve cover at the same time so I can flush the motor down with seafoam...will do this before i remove the oil pan, so that it doesn't just drain all over my face...

 

 

Mine too. Lift makes it sooo much easier. :D I do suggest letting the truck sit as long as possible before removing the pan. And even then, you'll have drops of oil falling on you while you work. Goggles and earplugs are recommended.

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'89 2.5, stick, can the RMS be replaced fairly easily without pulling anything major? I gotta clean all that oil off of everything (and I mean everything) from the block back. Oil is puddling directly under rear of the block.

 

Purple Stuff generously applied mainly to tranny (but away from harness plugs) and soaked in, sprayed away with hose (again away from electrics) would this hurt anything or is this not a good idea

 

I put clear tubing on the line from the airbox to the ("new" aluminum) valve cover, has some oil in it already (1 week), is this normal or what else do I need to look for to fix?

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'89 2.5, stick, can the RMS be replaced fairly easily without pulling anything major?

Nope -- sorry.

 

The RMS can be replaced on the 4.0L by just dropping the pan, because it's a 2-piece seal. For some inexlicable reason, they used a 1-piece seal on the 2.5L. You have to pull the tranny and flywheel to change it.

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Thanks Eagle, I was afraid of that answer. PO put a new clutch in and I'm betting never thought about the seal. I'm probably not the only one that feels that the engineers/designers should be cattleprodded :brows: when they come up with some of their ideas

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My truck has 15" of lift and i still replaced mine on the hoist at work. Did i mention i sell parts for mopar. factory rms, valve cover, open radiator, new fan all for less then 200 bux. plus i managed to get the seinor tech to don all but the rear main 4 me.

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after the breather vent was added, it's not leaking very much (have not added oil since the first time it leaked tho it leaks drops here and there, it does not puddle up and is still at full)

...so i'm going to do the valve cover gasket, then pressure wash the motor and up inside the bellhousing, then just leave it be.

 

there's very good potential that I will end up building a stroker...meaning money spent here would be wasted.

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