Oil Leak: Pan Gasket Or Rear Main Seal?

67CJ5 f134
Noticed a leak coming from the rear of the oil pan while running...couple of drops every few minutes. PO had engine rebuilt so I would think the seals would have been replaced (3k miles ago). Can't tell if the pan has a real gasket or just made from black magic. Lots of stuff squished out the sides. I am going to replace the pan gasket but am wondering if there is a way to determine if the rear seal should be replaced while I have the pan off?

Thanks for your ideas.
Bill

 

I’d start with replacing the pan gasket and see if that solves it but DO NOT over tighten the pan bolts, it can warp the pan (which may already be the case by the PO). I believe the pan bolts only get about 12 ft lbs. I could be off a bit but I know it’s not much. I put on a new Fel-Pro gasket and some RTV when I did my rear main seal and I’ve been pretty fortunate. Look at the rear of the block where it meets the transmission bell housing and see if oil is running down there anywhere or if it’s coming out from under the pan. When you do replace the pan gasket or rear main (or both), be sure not to cut off the dowels flush with the block-they should be hanging down an 1/8”-1/4” or so by the rear main cap. They hang lower than the block so when the pan is installed, they “squish” out making a tight seal. Don’t ask me how I know

 

Check for flatness or even a little relief around the pan bolt holes. Gently hammer them if necessary to be a bit hollow on the mating face.

 

This.

 

Just a suggestion, after I put a new motor in my Jeep, I took the motor I took out and made Garage out of it. I stripped it to bare metal and clear coated it, put new gaskets on it, new oil pan, side cover and valve cover, gaskets. After I got it running it kept "Spotting" right under the rear seal. It was running down the oil pan right in front of the rear motor plate, making me think it was a bad seal on the pan gasket. I pulled the pan, put it back on carefully, same thing dripping down the front of the rear engine plate, I finally figured out it was the rear main seal. Pulled the pan again replaced the rear seal, and pan gasket again, slow learner, now I have no leaks. What I learned is that if the rear seal is leaking it runs out between the rear engine plate and the oil pan. At least this one did. Good luck

 

thanks Guys for your reply's! looking forward to getting under her this weekend and replacing the gasket. Will keep you posted.

 

Timely post. I just did the oil pan gasket on my F134. Too soon to tell if the rear main seal is leaking also. Perhaps if I was more forward thinking I would have replaced the rear main seal while I was in there. Time will tell.

 

I was concerned about replacing my leaking rear main seal after hearing horror stories of trying it with the motor still in the Jeep but my old came out easily and my new one went in smooth as well with a little help of someone turning the motor over by hand to help pull it around the crank.

 

Do you remember what the torque for the oil pan nuts was? My manual says 39 ft lbs...way different than the 12 above?

 

Sure that wasn't inch-pounds?

Are they nuts, or bolts?

 

Yeah that's gotta be right. I put it back on this afternoon and the 12 felt right. Well know tomorrow when I refill the oil and start her back up!

 

Bolts. You're right though. Put it back on this afternoon and 12 felt right. Anymore and it felt like over tightening.

 

I don't use a torque wrench, I just pull the bolts until I feel that are tight enough, you don't want to over tighten cork gaskets, they will squeeze out and leak.

 

anyone know why the oil pan has a separation or baffle which divides it up about 2/3-1/3? I should have taken a picture when I had it off but envision a metal wall dividing it that way. oil still gets to the back 1/3 due to a small opening but i'm just curious. bh

 

in order to slow down fore and aft oil movement?

 

This. Otherwise the pick-up would be sucking air half the time.

 

That makes sense! Thanks