Rear main seal DIY

[Maxhouse97]

Part is on it’s way, could I reuse the bolts?

[George Hill]

The PN# for the M/S5x kit is different than the pn# for the S54 kit. Looking at the parts the bolts are shorter for the S54. There is no listed part number for the housing so we don't know just looking at the diagram if it is different. BUT if the housing is "thinner" the bolts would be shorter.

So YMMV but the M/S5x kit may not wok on an S54. I'll see if I can measure some today.

[bmwfnatic]

I believe only PTFE "new style" seal should be used on the S54 engine.

The chart below shows the best rubber seal (VITON or FKM on the chart) only can handle up to 7000 rpm for out cars, and I don't think those rubber seals with the spring on the lip are even VITON.
I assume the crank seal is 3.5" or 90mm diameter (guessing from visual memory), then the circumference = 2R PI = 283mm
At 8000 rpm the surface speed is 283mm * 8000/60 = 38m/s which is more than 35m/s that can handle by VITON seal.

PTFE seal has the lowest friction so I'm surprised to hear that it caused the deep groove. Maybe dust/dirt collected at the seal lip did the wear on the shaft, not the seal.

Pretty interesting man, I hadn't even thought about this part, you learn something every day.

[Maxhouse97]

Awesome thanks all, just ordered one

[sapote]

I don't like these 'new style' seals that BMW has switched to, also retroactively for older cars it seems.

Over time the front and rear main seals create a low spot on the crankshaft, you can feel this spot with your finger, it's quite pronounced.
If you install one of those new style tensionless seals, and your low spot it quite large, they will never seal, they leak.

I prefer to stick to the 'old style' seals with a spring inside them, they provide more tension and are more forgiving if the crank surface they are riding on isn't absolutely brand new.
A generic 110x90x12mm seal with the right properties and a spring is suprisingly easy to source.

I believe only PTFE "new style" seal should be used on the S54 engine.

The chart below shows the best rubber seal (VITON or FKM on the chart) only can handle up to 7000 rpm for out cars, and I don't think those rubber seals with the spring on the lip are even VITON.
I assume the crank seal is 3.5" or 90mm diameter (guessing from visual memory), then the circumference = 2R PI = 283mm
At 8000 rpm the surface speed is 283mm * 8000/60 = 38m/s which is more than 35m/s that can handle by VITON seal.

PTFE seal has the lowest friction so I'm surprised to hear that it caused the deep groove. Maybe dust/dirt collected at the seal lip did the wear on the shaft, not the seal.

https://advanced-emc.com/four-most-popular-rotary-shaft-seals-material-options-and-how-they-compare/

[bmwfnatic]

I don't like these 'new style' seals that BMW has switched to, also retroactively for older cars it seems.

Over time the front and rear main seals create a low spot on the crankshaft, you can feel this spot with your finger, it's quite pronounced.
If you install one of those new style tensionless seals, and your low spot it quite large, they will never seal, they leak.

I prefer to stick to the 'old style' seals with a spring inside them, they provide more tension and are more forgiving if the crank surface they are riding on isn't absolutely brand new.
A generic 110x90x12mm seal with the right properties and a spring is suprisingly easy to source.

[jpy1980]

You should watch FCP euros video on a clutch job. I think they address the RMS there too and tell you what tools you need

https://youtu.be/NmEOFBqreX8?si=__xYXyd_kgfwmCEv

[sapote]

They are all the same for m50/52, s54, etc. Seems like whole kit is harder to find. You can prob get them here for $144

https://www.bmwpartsfactory.com/GENUINEBMW/9/11-14-2-247-867

Sent from my SM-S911U1 using Tapatalk

This is the best deal at $144, as elsewhere sold for $359: https://www.bimmerworld.com/Engine/G...142247867.html

[mrgizmo04]

They are all the same for m50/52, s54, etc. Seems like whole kit is harder to find. You can prob get them here for $144

https://www.rmeuropean.com/Products/11142247867-MFG9-V130.aspx

https://www.bmwpartsfactory.com/GENUINEBMW/9/11-14-2-247-867

Sent from my SM-S911U1 using Tapatalk

[Maxhouse97]

Starting a new thread related to a nearby clutch thread. I have been told that you can either buy a rear main seal assembly or a tool in order to install it to the correct depth. I cannot find the assembly for sale, is it still available? If not, the tool is for sale for $120. Does anyone have the tool available to lend, I’m willing to pay shipping. Thanks.