Rear Main Seal?

OK, can someone please tell me why after only ten thousand miles and just a little over two years is my rear main seal gone bad again. The first time I had it fixed was from the dealership in Sterling VA under CPO..... So I called the dealer to see if it was still under warranty and of course they said the warranty for that is for only two years. Of course ten months short, A day late and a dollar short!!!! The part that frustrates me the most is that after I finally get my suspension problems worked out this happens. I feel like sometime I just can't catch a break with this car. You fix one thing and "BAM" something else breaks. OK enough complaining... do anyone know why this is?

Thanks
Mike

Are you sure it the rear main? That is not a common failure point on that engine. Who diagnosed it and how?

Originally Posted by chiefwej

Are you sure it the rear main? That is not a common failure point on that engine. Who diagnosed it and how?

Actually, I looked at it myself. The last time I had the rear main seal go bad I took the bell housing plugs out and you can see where the oil is leaking. This time what I'm also seeing again by looking up in the holes in front of the fly wheel is oil coming from the front of it.

Where is the rear main seal? I have a leak after changing my valve cover gaskets and I'm pretty sure it's not the gaskets?

Originally Posted by Al's540i

Where is the rear main seal? I have a leak after changing my valve cover gaskets and I'm pretty sure it's not the gaskets?

Behind the flywheel/flexplate on the block.

Originally Posted by Ryan M

Behind the flywheel/flexplate on the block.

IS it hard to change out? Would I need to take it into a shop??

IF it is my rear main seal, is it easy to tell if that's whats leaking?

Originally Posted by Al's540i

IS it hard to change out? Would I need to take it into a shop??

IF it is my rear main seal, is it easy to tell if that's whats leaking?

Well, it's behind the flywheel, so you'd have to remove the transmission, pressure plate, clutch disk, flywheel, and finally the seal. It's a lot of work. If you don't have a lift or don't feel 110% confident in your abilities or experience, it's a job best left to the pros. You also need a few special tools for the job.

If you see oil leaking from the bottom of your bellhousing, there is a good chance the rear main is leaking.

Originally Posted by Ryan M

Well, it's behind the flywheel, so you'd have to remove the transmission, pressure plate, clutch disk, flywheel, and finally the seal. It's a lot of work. If you don't have a lift or don't feel 110% confident in your abilities or experience, it's a job best left to the pros. You also need a few special tools for the job.

If you see oil leaking from the bottom of your bellhousing, there is a good chance the rear main is leaking.

IS the bell housing what sits in front of the transmission...or is that the torque converter?

my rear main is leaking too. but i think most of the leak is from the oil pan gasket

Originally Posted by BMW5MT

OK, can someone please tell me why after only ten thousand miles and just a little over two years is my rear main seal gone bad again.
Thanks
Mike

Originally Posted by BMW5MT

most likely because the install was not done right..

Originally Posted by Al's540i

IS the bell housing what sits in front of the transmission...or is that the torque converter?

The bellhousing is what houses the flexplate and torque converter in an auto, and houses the flywheel, clutch, pressure plate, and throwout bearing in a manual trans. It is connected to the tranny and bolts directly to the block.

The red arrow points to the bellhousing.

Originally Posted by kishg

most likely because the install was not done right..

I'm trying to rap my head around how something like a seal that last for 10K miles and over two years wasn't installed correctly. I would think if it wasn't installed correctly after the initial install, you would very soon after get a leak
not two years later.

Correct diagnosis is they key. How many miles in your car?

In my 1983 E23 735i 5spd, the Rear Main Seal leaks at 130K, the FRONT Man Trans Seal leaked at 140K miles.
I suspect you have man trans oil seals leak.

Wipe the whole area dry, drive a short while and look again. The problem is: the engine oil and man trans oils look very similar and almost impossible to tell the difference.
(In contrast, if one has an AUTO trans, then the auto trans fluid usually has a red dye that can tell you it is ATF).

Google for "engine oil dye", I think there is a dye you can put in engine oil to trace leaks.

The dealer should have changed ALL 4 seals in the man trans when it was removed from the car for the RMS leak.

Are you losing oil or trans fluid? Checking both would be a good idea.

Originally Posted by cn90

Correct diagnosis is they key. How many miles in your car?

I have about 86K miles on my car. The fluid thats leaking don't smells like transmission fluid. To me it smells like regular oil.

OK let me ask this question! If my car is leaking fluids from the bell housing when the engine is just running wouldn't that be the RMS because that seal is on the engine side? That is what my car is doing. I would think that the only time I would see that the Man Trans Seal would be leaking is if I had the car in gear and driving the car with the transmission turning right. Wouldn't that be the seal on the transmission side?

I will also take some pictures inside the bell housing through the plug holes.

The hole at the bottom of the bell housing drains any fluid that gets inside:
- leaking RMS
- Leaking slave cylinder
- leaking FRONT INPUT shaft seal of the man transmission.

Research on tracing dye, easy to do.

Originally Posted by cn90

The hole at the bottom of the bell housing drains any fluid that gets inside:
- leaking RMS
- Leaking slave cylinder
- leaking FRONT INPUT shaft seal of the man transmission.

Research on tracing dye, easy to do.

Can automatic tranny fluid get in there and leak from that hole?

Originally Posted by Al's540i

Can automatic tranny fluid get in there and leak from that hole?

It's possible. The input shaft seal could leak and ATF could run out of the bellhousing. What does the fluid look/smell like?

Originally Posted by Ryan M

It's possible. The input shaft seal could leak and ATF could run out of the bellhousing. What does the fluid look/smell like?

Well, the reason i ask is because I drained/refilled my tranny yesterday but when I was draining, I wasn't draining at temp so I think i may have overfilled the tranny. Now I have a leak there. I alwasy had hanging drops there that never actually dropped to the floor but now I have several drips from that area.

I didn't have time to investigate today, maybe tomorrow but I think it might be ATF...of course oil and new ATF mixed with old dark ATF look the same.

Originally Posted by Al's540i

Well, the reason i ask is because I drained/refilled my tranny yesterday but when I was draining, I wasn't draining at temp so I think i may have overfilled the tranny. Now I have a leak there. I alwasy had hanging drops there that never actually dropped to the floor but now I have several drips from that area.

I didn't have time to investigate today, maybe tomorrow but I think it might be ATF...of course oil and new ATF mixed with old dark ATF look the same.

If you can, wipe the area clean with some type of solvent and a rag. Then, check the area again after some time, and you should get a good reading of what color the fluid is.

Originally Posted by Ryan M

If you can, wipe the area clean with some type of solvent and a rag. Then, check the area again after some time, and you should get a good reading of what color the fluid is.

If it's ATF, could my overfilling be causing this leak? and If so, will a 2nd drain/refill at temp fix the leak?

Originally Posted by Al's540i

If it's ATF, could my overfilling be causing this leak? and If so, will a 2nd drain/refill at temp fix the leak?

Yes and yes. Clean the area, then put some paper towel or other white paper under the car. Check later for stains, auto trans fluid should be red.

Originally Posted by chiefwej

Yes and yes. Clean the area, then put some paper towel or other white paper under the car. Check later for stains, auto trans fluid should be red.

While I agree with this statement on other vehicles, BMW OEM ATF is a light brown color...kinda like the color of a light beer. That's why many times it's hard to distinguish between used ATF mixed with new and oil.

But thanks for that response, i'll monitor the situation and if it keeps up I"ll definitely do another drain/refill.

This thread points to the necessity of good mechanic fore-sight: whenever the transmission is removed from the car for whatever reaons, take care of all the seals (even they are not leaking) because of the labor costs (seals are cheap but labor of removing trans very expensive).

1. Clutch Job: do the clutch but a good mechanic will ALSO replace:
- Engine's RMS
- Man Trans seals x4
(Auto Trans seals x3)

2. Changing transmission, same deal as #1.

3. Replacing RMS, same deal as #1.