Rear main seal keeps leaking

Kvarilek

Kvarilek

TJ Enthusiast
Joined
Aug 1, 2018
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117
Location
Harrisburg, SD
Several months back I replaced my motor mounts with Brown Dog mounts. A few weeks after I started having a rear main seal leak. I took it to the local mechanic and he did the replacement. Well, it started leaking again immediately. Took it back and he replaced it again. That lasted about a day and it leaked again. So now after being replaced a third time it's again leaking.

My question is could it stem from replacing the motor mounts? The install was kind of a bugger and it took using ratchet straps to get the motor in position for the bolts to line up. Could things now be out of whack which is causing this?
 
por212 said:
I would suggest verifying oil is not leaking from your valve cover in the back of the engine. Valve cover leak in the back of the engine could make things look like your main seal is leaking.
Click to expand...
This! The valve cover is leak prone. It will look like a rear main if not investigated from the top of the engine down.
 
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Kvarilek said:
Several months back I replaced my motor mounts with Brown Dog mounts. A few weeks after I started having a rear main seal leak. I took it to the local mechanic and he did the replacement. Well, it started leaking again immediately. Took it back and he replaced it again. That lasted about a day and it leaked again. So now after being replaced a third time it's again leaking.

My question is could it stem from replacing the motor mounts? The install was kind of a bugger and it took using ratchet straps to get the motor in position for the bolts to line up. Could things now be out of whack which is causing this?
Click to expand...

as they say^.
but also yes, if you forced up the engine and did not release the bind in the rest of the drive line. it has to move somewhere.
 
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Loosen both motor mounts and the tranny mount. Give everything a good shake to let it find where it wants to be and tighten them all back up. This should relieve any tension between the mounts. But it is unlikely that the rear seal leak is caused by new mounts.
 
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Ask your mechanic if he use anaerobic sealant. If he used regular sealant on the bearing cap it will leak.
 
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If you are running a synthetic engine oil try switching to a high mileage conventional oil like Mobil Super. My BMW's RMS was leaking bad so I switched from Castrol synthetic oil to Mobil Super and the RMS stopped leaking in a couple days. High mileage engine oils like Mobil Super contain additional seal conditioners. For sure engines tend to leak more easily with synthetic engine oils.
 
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Thanks guys! I'll check with the mechanic and dive in to the specifics of what he did. I've rubbed my hand around the valve cover and it's definitely dirty but doesn't seem like a lot of oil. The last time he worked in it I mentioned he should check that and he didn't think that was the issue. I'll have to do some follow up with him.
 
This is far out there, but I had sort of the same issue, I replaced my rear main seal because I thought it was leaking too. It left a drop on the floor where the trans and engine bolted together. I took the pan off and replaced the rear main and minutes later same drop on the ground. I thought maybe I had a scored crank as it is possible you do, but in my case I went down and looked at everything and properly diagnosed it after I already replaced it for no reason.

Here was the issue with mine, all of my soft (freeze) plugs were leaking on the side of the block. I know you are saying well that would be green. Well you would think so, but it mixed with the dirt and grime on the block, and by the time it hit the ground just looked like dirty engine oil. I ended up replacing all of my soft plugs. So probably not your issue, but wanted to throw it out there because it was definitely my issue. A slight leak on a soft plug with a dirty engine looks like a rear main leak.

That said if yours is truly a rear main leak, and they just keep doing it over and over, maybe the crank has a scratch where the seal goes or maybe the seal wore a groove in it. If it is truly leaking, it needs to be really inspected for issues at the crankshaft where the seal goes in my opinion.
 
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