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2 years ago during the annual service at the local dealership the diff oil was changed, a day or two later I noticed oil on the drive underneath the rear, the muppet who did the job hadn’t tightened both filler and drain plugs, car was returned and it was rectified, needless to say the next service was done at a different dealership, it’s started leaking again, could it have been cross threaded.
2 years ago during the annual service at the local dealership the diff oil was changed, a day or two later I noticed oil on the drive underneath the rear, the muppet who did the job hadn’t tightened both filler and drain plugs, car was returned and it was rectified, needless to say the next service was done at a different dealership, it’s started leaking again, could it have been cross threaded.
Maybe they didn’t perform a proper cleaning of the residual oil after service? They may have very well cross-threaded the plugs. My suggestion would be to get some soapy water solution going and spray the entire differential case and allow to dry. You can also use brake parts cleaner from the local auto parts store amd get that oil cleaned up. Drive 20 miles then re-check where the leak is coming from.
Maybe they didn’t perform a proper cleaning of the residual oil after service? They may have very well cross-threaded the plugs. My suggestion would be to get some soapy water solution going and spray the entire differential case and allow to dry. You can also use brake parts cleaner from the local auto parts store amd get that oil cleaned up. Drive 20 miles then re-check where the leak is coming from.
I watched a video of it after it was done the second time and it was all clean, I’m not entirely sure but I think it’s a fairly course thread on the plugs and you’d have to be pretty incompetent to achieve it anyway after a ‘conversation’ with the service manager the vehicle is going back to them on Tuesday because if it is cross threaded I can’t imagine the cost of fixing that, good suggestion to see where it came from but I’ve got too old to get under the car, the photo was taken at the MOT annual inspection.
I watched a video of it after it was done the second time and it was all clean, I’m not entirely sure but I think it’s a fairly course thread on the plugs and you’d have to be pretty incompetent to achieve it anyway after a ‘conversation’ with the service manager the vehicle is going back to them on Tuesday because if it is cross threaded I can’t imagine the cost of fixing that, good suggestion to see where it came from but I’ve got too old to get under the car, the photo was taken at the MOT annual inspection.
*****I've done my own differential fluid change on my 2018 C63s and the threads are indeed quite coarse. I don't remember there being any type of washer on the plugs (there are two), but if there are, I'd replace them if it is leaking. That being said, it shouldn't leak and it would be tough to cross thread those bolts unless the tech is a complete moron.
That being said, if it does still leak, get the fluid replaced again (it's very cheap relative to other fluids like the trans fluid..) and have the tech use pipe dope or teflon tape as an additional barrier to help prevent leakage. You really don't want to have low differential fluid from a leak, much less on an electronic lock differential which is kind of sensitive to that. Cheap insurance.
*****I've done my own differential fluid change on my 2018 C63s and the threads are indeed quite coarse. I don't remember there being any type of washer on the plugs (there are two), but if there are, I'd replace them if it is leaking. That being said, it shouldn't leak and it would be tough to cross thread those bolts unless the tech is a complete moron.
That being said, if it does still leak, get the fluid replaced again (it's very cheap relative to other fluids like the trans fluid..) and have the tech use pipe dope or teflon tape as an additional barrier to help prevent leakage. You really don't want to have low differential fluid from a leak, much less on an electronic lock differential which is kind of sensitive to that. Cheap insurance.
Good luck
Good point, I’ll mention that when I take it in today.
They say it’s drive shaft oil seal leaking, I went to look at it when it was on the lift and it does look like it but not enough for the amount showing, it’s out of warranty so it’s going to cost.
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