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RMS (rear main seal) -- Question & Advice...

5K views 20 replies 8 participants last post by  Kevin The Clean 1 
#1 · (Edited)
My RMS has been leaking ever since I bought my M5. I'm finally at the point where I'm deciding to take care of it. While I drop the exhaust & transmission I will be putting in a brand new CNS racing clutch as well. My question is (since I have only seen people work on their M5 rear main seals in videos & in pictures) I'm not sure exactly what it looks like & what the actual part numbers are. THANK YOU in advance for your time & help...



RealOEM.com * BMW E39 M5 Engine Block Mounting Parts

Is it #7 & #8 that I want to replace in this diagram above ^^^... ?



RealOEM.com * BMW E39 M5 LOWER TIMING CASE

Or is it #6 & #7 in this "other" diagram above ^^^... ?







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#2 ·
It's 6, 7 & 8 in the first link - if you want to change the carrier too. You can change only the actual seal (7) although some people recommend installing the seal pre fitted in the carrier. Others may chime in with advice on this...

The second link is the front seal around the harmonic balancer.

Nick
 
#6 · (Edited)
IN the next few weeks but there is no way I would be doing this myself. I've done 95% of the work on my M5 but dropping the tranny & putting in a new clutch is way too much work for me. I don't want to mess up the install of my CNS Racing clutch & new RMS. I'm not sure who I will have install it yet but I'm researching right now who I want to have the work done by...

Just buy this part number (#6 on your first link) and you will have everything you need for the rear main seal job. Plus, the seal comes already installed. All you have to do is tighten it up. Comes with #11 too (see your first link) which also leak oil.

John
That is the part I will order then (#6) which seams to come as a kit... Thanks so much.

To everyone else, thanks for the help as well. I really do appreciate it... :cheers:




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#10 ·
This.....

Make sure you put a very thin layer of RTV on the bottom of the flange.

If you are feeling sparky, I would replace all 4 CPS's while you have the transmission out. They are a complete PITA to get to from the top side, but UBER easy to get to with the transmission out.
 
#5 ·
I've done both the 540i and the M5 RMS. Never bought the carrier as I've got a press and made a drift to press it into the carrier. But, all the other parts are a must have.

My advice on doing it is to a) watch the bolts from the oil pan that hold the carrier down (eg, don't force the carrier off without removing all the bolts!), b) clean all surfaces.

c) You may have scoring on the crank, it's probably fine even if it's noticeable (I've put 60K on one that looked terrible and still no new leakage).

d) When installing the carrier/seal besure to lube up both the crank and the seal. Work hard to press evenly and have the lip seal go over the end of the crank all at once. You can't twist it due to the oil pan but as long as it goes on uniformly it will be fine.

YMMV and Good Luck!
 
#12 ·
Mine was just done at 91k. +1 on getting the whole piece #6, +1 on the RTV like Timmy mentioned, and +1 on the CPS. If you can wait a lil longer and save for them and do it at once it will be worth it. I would have replaced mine at the same time but previous owner did at 70K.
 
#13 ·
Is there a certain life span for these CPS's or a certain replacement interval on these that I was not aware of / know about... ? 02 sensors have a certain "useable" life & various other parts that I was well aware of. But these CPS's are relatively new to me (although I have heard people mention them & talk about them) quite often. I just thought they were a part that was (replace only if they are bad) kind of sensor.

Please provide me with part #'s to Realoemparts.com is possible so I can look into in further (if need be)...
 
#19 · (Edited)
To my understanding, you don't know how bad they are until they fail. Again, to my understanding, they do "wear" over time, robbing you of a few HP. I can understand the logic of not fixing something that isn't broken, so if you are happy with it, then so be it. If you wanted the most out of your car, then I would suggest replacing them. Preventative maintenance. You see so many people on here (the forum) replacing parts that don't need replaced, but when it comes to something like CPS's, you just don't know if it will make a difference or not.........
 
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