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Discussion Starter · #1 ·
My 66 plate pre LCI went in for its MOT and 5th year brake fluid change on Friday. The vehicle health check picked up a leaking diff input shaft seal :roll: .

It's weeping rather than dripping so not developed into a bad leak yet fortunately. They said the oil level was ok but i'll be asking for a fluid change when it's repaired.

Been quoted £425 which is 90% labour!!

A quick google found that this is quite a common issue on early F8x cars so worth having a look underneath to check for anyone with a pre lci car.

On mine you could see oil on the diff fins.
 

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Discussion Starter · #3 ·
M2_BabaYaga said:
Found myself the same issue today when in for custom exhaust consultation

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Not good. I'm hoping a new seal is a reliable fix and that there aren't any problems for the drive side and non drive side.
 

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Discussion Starter · #5 ·
I'm sure if you had access to ramps and were handy with spanners this could be a diy.

No way I'd be trying it on my driveway though personally. The service advisor said he had seen a few of these on M240s and X5s and said sometimes it needs two mechanics on a breaker bar to release the main nut. No idea if that is true though!
 

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I have a weeping diff on my M2 too, apparently it's the front sensor leaking on mine. It's going in to get sorted on Monday, service guy said the warranty will cover it
 

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Discussion Starter · #10 ·
turvytopsy said:
I have a weeping diff on my M2 too, apparently it's the front sensor leaking on mine. It's going in to get sorted on Monday, service guy said the warranty will cover it
It looks like quite a common issue unfortunately. I'll try to see if I can get some goodwill from BMW although I'm doubtful.

My worry is the reliability of the other seals as well as the replacement.
 

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First time I've been under my car since I got home and it would appear mine has a leak. Looks like the the same case as turvytopsy and it's the front sensor, the sensor is quite wet but above it is dry so doesn't appear to be the prop shaft seal. Should there by a very very slight whine at low speeds from these diffs?
 

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Discussion Starter · #12 ·
It is normal to have a slight whine at low speeds on this diff. Hopefully you've caught it early though and not much fluid lost.

Mine was repaired at BMW Bowkers Preston and top marks to BMW who knocked 50% off the repair as goodwill 👍
 

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The most annoying thing is that I've just bought it approved used. Surely they would have seen the leak! I guess it's a case if it would likely not become an issue until after the 12 month warranty is up so they don't really care. I don't get it though, they put new brakes all round and new front tires. I suppose these are things a customer will see, they don't bargain on people checking underneath.

I'll monitor it the next few days and see how wet it gets. There wasn't that much oil trailed down the fins so maybe it's not much that has actually leaked out. The oil looked to be golden in colour also, it points towards the oil having been changed at some point recently as all the videos of oil changes it's usually dark in colour. I would usually just buy a sensor and do an oil change while at it but this time I'm making a point of going through BMW. Hopefully that way if the oil has got low and there are issues after the warranty I can try and argue that's it's damage done due to an obvious leak being missed or ignored during their ever so stringent used car checks…

I assumed the whine was ok since the subframe and diff are fairly solidly mounted to the chassis but did wonder if maybe the oil has got too low and damage is already done. I remember watching Misha Charoudin's video from when they but solid bushings in the diff mount on Apex Taxi's M2, the whine made it sound like a DTM car.
 

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MarkmacRS said:
The most annoying thing is that I've just bought it approved used. Surely they would have seen the leak! I guess it's a case if it would likely not become an issue until after the 12 month warranty is up so they don't really care. I don't get it though, they put new brakes all round and new front tires. I suppose these are things a customer will see, they don't bargain on people checking underneath.

I'll monitor it the next few days and see how wet it gets. There wasn't that much oil trailed down the fins so maybe it's not much that has actually leaked out. The oil looked to be golden in colour also, it points towards the oil having been changed at some point recently as all the videos of oil changes it's usually dark in colour. I would usually just buy a sensor and do an oil change while at it but this time I'm making a point of going through BMW. Hopefully that way if the oil has got low and there are issues after the warranty I can try and argue that's it's damage done due to an obvious leak being missed or ignored during their ever so stringent used car checks…

I assumed the whine was ok since the subframe and diff are fairly solidly mounted to the chassis but did wonder if maybe the oil has got too low and damage is already done. I remember watching Misha Charoudin's video from when they but solid bushings in the diff mount on Apex Taxi's M2, the whine made it sound like a DTM car.
Oil leaking from my diff was golden after 17k miles.
 

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I had the same issue with my old f80 m3. Spotted it on the ramp having an alinement done strangely just after it had come back from a service from the dealer where they had missed it.

Bought the car from a dealer not bmw. They were happy for me to book the car in and have the work done under warranty and they would pay for it. Even after pointing out the leak to the bmw dealership they explained it was "misting" and they recommended not change it. I argued the toss with them saying misting or not a leak is a leak and had the work done. £6500 later a new diff and carbon prop were fitted into the car under "goodwill" not sure what happened to need a new diff but I wasn't complaining. Seems the f8x diffs aren't the best

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Connar92 said:
I had the same issue with my old f80 m3. Spotted it on the ramp having an alinement done strangely just after it had come back from a service from the dealer where they had missed it.

Bought the car from a dealer not bmw. They were happy for me to book the car in and have the work done under warranty and they would pay for it. Even after pointing out the leak to the bmw dealership they explained it was "misting" and they recommended not change it. I argued the toss with them saying misting or not a leak is a leak and had the work done. £6500 later a new diff and carbon prop were fitted into the car under "goodwill" not sure what happened to need a new diff but I wasn't complaining. Seems the f8x diffs aren't the best

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I would guess they drained the oil and a decent amount than the +/-1ltr that should be in there came out so they changed the diff as a precaution.

I'm not fussed either way with mine. Like I say at least me raising concerns and booking it in for the issue will be in the system. Due to the sensor locator dropping the oil will be part of changing it out so I'll be asking how much comes out if they don't tell me. If the oil is low I'll be pushing for it to be documented if not a new diff. I'm not potentially getting getting stung with a big bill down the line.
 

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MarkmacRS said:
I would guess they drained the oil and a decent amount than the +/-1ltr that should be in there came out so they changed the diff as a precaution.

I'm not fussed either way with mine. Like I say at least me raising concerns and booking it in for the issue will be in the system. Due to the sensor locator dropping the oil will be part of changing it out so I'll be asking how much comes out if they don't tell me. If the oil is low I'll be pushing for it to be documented if not a new diff. I'm not potentially getting getting stung with a big bill down the line.
Mark - if yr car goes in for warranty and this involves removing the diff, something to consider...

1. get techs to assess rear diff mount bush - n55 engined cars all have single rubber bush which is know to perish/crack -
2. S55 M2C's all came with poly bush from factory so BMW swap out failed rubber bushes for the newer oem poly bush.
3. Even if the techs report rubber bush is OK, if I were you, I'd be inclined to pay for the part and the extra labour to have rear poly bush installed, asumming labour for diff removal/refit labour is covered by leak remedy warranty work.

BP
 

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Mark - if yr car goes in for warranty and this involves removing the diff, something to consider...

1. get techs to assess rear diff mount bush - n55 engined cars all have single rubber bush which is know to perish/crack -
2. S55 M2C's all came with poly bush from factory so BMW swap out failed rubber bushes for the newer oem poly bush.
3. Even if the techs report rubber bush is OK, if I were you, I'd be inclined to pay for the part and the extra labour to have rear poly bush installed, asumming labour for diff removal/refit labour is covered by leak remedy warranty work.

BP
[/quote]

Thanks for the heads up.
 

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MarkmacRS said:
Connar92 said:
I had the same issue with my old f80 m3. Spotted it on the ramp having an alinement done strangely just after it had come back from a service from the dealer where they had missed it.

Bought the car from a dealer not bmw. They were happy for me to book the car in and have the work done under warranty and they would pay for it. Even after pointing out the leak to the bmw dealership they explained it was "misting" and they recommended not change it. I argued the toss with them saying misting or not a leak is a leak and had the work done. £6500 later a new diff and carbon prop were fitted into the car under "goodwill" not sure what happened to need a new diff but I wasn't complaining. Seems the f8x diffs aren't the best

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I would guess they drained the oil and a decent amount than the +/-1ltr that should be in there came out so they changed the diff as a precaution.

I'm not fussed either way with mine. Like I say at least me raising concerns and booking it in for the issue will be in the system. Due to the sensor locator dropping the oil will be part of changing it out so I'll be asking how much comes out if they don't tell me. If the oil is low I'll be pushing for it to be documented if not a new diff. I'm not potentially getting getting stung with a big bill down the line.
I know when they test drove it after the work the diff came back whining. I think they fubar'd the diff and then swapped it out no questions asked.

That the reason I didn't want to do the work myself. Didn't fancy issues down the line i had to explain. Bmw in all fairness were really good about the whole thing. The car wasn't purchased through them and it was 3 months outside its manufactures warranty and they still sorted it. I was happy with a brand new diff! Just was told to go reasonably gentle on it being new

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My car was in the dealership November for them to clean the diff off and back into them yesterday for them to access the severity of the leak. Apparently it's not bad enough for BMW to accept a warranty claim. So looks like they expect me to foot the bill once it gets bad enough, likely out if warranty. I find it strange how I cleaned it when I seen it initially after a few days of ownership, a few days later it was just as moist again. It goes into BMW they clean it and it's as good a bone dry. I can only think it's either fixed itself, the cold weather is making the oil stay slightly more viscous masking the leak or the level is low enough to stop the leak, I guess that would mean the diff was nearly bone dry though.

When is the diff service on these diffs? 3rd or fourth oil service? I'm inclined to pay to get it done and ask them to measure the amount of oil that comes out so I know what's going on. I might speak with BMW UK to see if this is a viable option to access the issue.
 
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