Rear main oil leak

Very
20170325_174855.jpg

Just did mine a couple weeks ago
 
It is VERY common on the 4.0 for that to leak. I had to install a new clutch so I had mine repaired at the same time.
 
bobthetj03 said:
Stupid common sadly. Mine has leaked from the day I purchased it. Not enough to make me want to fix it though.
Click to expand...


Mine leaves a dime sized spot after sitting overnight, but I've wiped it down and it won't leak while running and I'm watching. I suspect it's the rear main seal, but not really sure yet.
 
xxdabroxx said:
You might also check the valve cover gasket. I thought I had a RMS leak but it was the valve cover gasket.
Click to expand...

This. A leaky valve cover gasket will cause an oil drip in about the same spot a leaky RMS will. I had a leak that I assumed was the RMS for years, turns out it was the valve cover gasket.

To check, just run your hand along the back of the engine where the valve cover and block meet. If you come back with some oil on your fingers replace the gasket first. It's easy-peasy and a lot less messy than dropping the oil pan.
 
  • Like
Reactions: 94c2500
I have the same issue, don't know if it is the valve cover gasket or the rear main seal. I just wiped this off the back of the gasket (between the firewall and the cover). Does this mean the leak is from the gasket and not my main seal? Nothing was wet behind the core thought and it's pretty way and funky all throughout the oil pan and where the main seal is..
48211b58413590dc49c1835a0f01ee0f.jpg
 
Last edited:
I have already replaced the valve cover gasket hoping that was the problem. Looks like the RMS is next. Is one brand of seal better than another ?
 
spider said:
I have already replaced the valve cover gasket hoping that was the problem. Looks like the RMS is next. Is one brand of seal better than another ?
Click to expand...

I can't say with any certainty. What's more important is properly seating the seal.

The rear main seal on the 4.0 was a bad design to begin with.
 
Very common, the mechanic who fixed mine had just fixed one a few weeks before. I think I caused mine by changing the oil to a synthetic. Good thing is you can fix without pulling the engine.


Sent from my iPhone using Tapatalk
 
dylansalrin said:
I have the same issue, don't know if it is the valve cover gasket or the rear main seal. I just wiped this off the back of the gasket (between the firewall and the cover). Does this mean the leak is from the gasket and not my main seal? Nothing was wet behind the core thought and it's pretty way and funky all throughout the oil pan and where the main seal is.. View attachment 14353
Click to expand...

YES! YES! YES!

With the gunk you found, and where you found it you should absolutely degrease your engine and replace your valve cover gasket before even thinking about a rear main seal replacement.

I can't stress this enough. My 4.0l was "marking it's territory" bad enough that I was SURE I needed to change my rear main. It's not that bad a job, just a general PITA. I replaced my valve cover gasket and basically have no more drip. For sure it's not enough that I'm worried about it.
 
  • Like
Reactions: 94c2500
Top Bottom
Back