Need Advice on Changing Rear Main Seal

[RayC.]

Been having problem trying to solve an oil leak problem. I have already had the valve cover gasket, oil pan gasket and (at Winfred's suggestion) oil cannister housing seal changed in hopes of stopping this pesky oil leak. Unfortunately after doing the work there is still a leak. A friend looked at it and suggested that the only thing remaining may be the rear main engine seal. Is changing the rear main seal a big job and does anyone have any advice or tips to change this seal?

Thanks,

-Ray
'94 525 ia

[Jeff N.]

...if you're not clear where the oil's coming from, a dye test is a cheap way to locate the source. Essentially, a shop puts in a UV dye into the oil and you drive the car for a bit. Then they use a UV light to spot flourescent spots - aka sources of leaks. I can't imagine this service being more than about $75 or so.

The rear main is the seal at the back end of the engine sandwhiched between the tranny and the block. $10 part and 4 to 6 hours of professional labor, more if you DIY. It could be the source of the leak but you want to really be sure before you spend the cash to go after it.

My vote if you can't find the leak: Do a dye test.

Jeff
90 535i
No more oil leaks thank you.

[Kalevera]

Ray, how about some more info?

Like winfred suggested, the seal at the canister can make for some fun leaks. The one that everyone overlooks, and lots of people mess up when doing a pan gasket, is the dipstick tube O ring.

Most idiots will stick the O ring in the pan, and then jam the tube on top of it, effectively cutting it in two. Engine runs for a while and the thing spits out a nice little leak. Correct way to do it: O ring goes on the tube, lube the tube and ring, gently slide it into place, and it should seat with a light thunk. We've fixed three of these in the past few weeks due to incompetent pan gasket jobs.

To check the ring, get under the car (no way to see past the motor mount from up top) with an angled mirror...best kind is on an extendable stick...and have a look. If the leak is on that side of the block/from that area, and the other jobs were competently done, I'd suspect the O ring first and foremost


best, whit

[Bellicose Right Winger]

I was having trouble with oil leaks in my '93 525iM. Turned out the 1/4" hose that evacuates the crankcase had broken at the connection underneath intake manifold. This hose and the 5/8" hose that provides fresh air to the crankcase connect to engine at the front of the valve cover.

Paul Shovestul



Been having problem trying to solve an oil leak problem. I have already had the valve cover gasket, oil pan gasket and (at Winfred's suggestion) oil cannister housing seal changed in hopes of stopping this pesky oil leak. Unfortunately after doing the work there is still a leak. A friend looked at it and suggested that the only thing remaining may be the rear main engine seal. Is changing the rear main seal a big job and does anyone have any advice or tips to change this seal?

Thanks,

-Ray
'94 525 ia

[WarrenBrown]

I did the pan gasket on mine and had a leak afterwards. I pretty much followed Whit's instructions for replacing the o-ring. I still had the damaged during installation, enough so that it would several drops of oil a week which would end up towards the bell housing due to air flow.

You can get the dye that was mentioned at NAPA for 3 or 4 dollars, you will need a special light (black light?).

Warren
91 318is
95 525iT

[RayC.]

Thanks all for the advice. Will try the dye this weekend after checking the dip stick.

-Ray