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W204 rear main seal replaced, still leaks

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Old 07-23-2022, 03:52 PM
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W204 c250 cgi petrol facelift saloon
W204 rear main seal replaced, still leaks

Looking for advice, based in the UK, the rear main seal was replaced a couple of days ago by a reputable Mb specialist, checked car underneath today and it's still leaking

I'm trying to understand how it could still be leaking? Any advice would be appreciated

Does anyone have the official mb repair procedure for this job?

I read on another post different Mercedes model though that sealant should be added to the mount plate, would that apply to this vehicle?

W204 CGI petrol c250 saloon facelift blue efficiency

Last edited by ash1212002; 07-23-2022 at 03:56 PM.
Old 07-23-2022, 11:11 PM
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MY'14 W212 M276 3.5NA @60kMi
rear leak

what color is that puddle: engine oil... not ATF for sure, right?

The best thing about paying professionals for automobile repairs is parts & labor are guaranteed.

Engine rear leak could be from eay up high: the rear plastic camshaft seals that popped with high crankcase pressure (PCV!)
Old 07-23-2022, 11:26 PM
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Originally Posted by CaliBenzDriver
what color is that puddle: engine oil... not ATF for sure, right?

The best thing about paying professionals for automobile repairs is parts & labor are guaranteed.

Engine rear leak could be from eay up high: the rear plastic camshaft seals that popped with high crankcase pressure (PCV!)
It's definitely the rear main as no signs of oil further up the vehicle, pic attached
I'm trying to understand what would have caused it to leak again?


Old 07-23-2022, 11:34 PM
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MY'14 W212 M276 3.5NA @60kMi
heavy leaking

Your leak looks very active, not just a casual drip.

What mileage is the engine?
Old 07-23-2022, 11:38 PM
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Originally Posted by CaliBenzDriver
Your leak looks very active, not just a casual drip.

What mileage is the engine?
61k the garage replaced the rear main seal a couple of days ago. I've probably driven 70 miles since and thought I'd check if it was dry and lo and behold it's still leaking!

It was an expensive repair, I can only presume they may have not fitted the seal correctly? Or may not not have used the sealant on the cover?

Would be good to see what the official mb repair procedure is for this job
Old 07-23-2022, 11:44 PM
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procedure check...

great idea to check the procedure. MB may have inserted an extra step to ensure good a seal vs. what you got.

In any case: WARRANTY time! They charge premium prices for premium results.
Old 07-23-2022, 11:46 PM
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Originally Posted by CaliBenzDriver
great idea to check the procedure. MB may have inserted an extra step to ensure good a seal vs. what you got.

In any case: WARRANTY time! They charge premium prices for premium results.
Will be on the phone to them first thing! If anyone has the official repair procedure please kindly provide

Thanks!
Old 07-24-2022, 08:28 PM
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Originally Posted by ash1212002
Will be on the phone to them first thing! If anyone has the official repair procedure please kindly provide

Thanks!
Here is the WIS procedure for replacing the seal which does involve the use of sealant.

Attached Files
File Type: pdf
Crankshaft Seal Replacement.pdf (417.6 KB, 221 views)
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Old 07-24-2022, 08:48 PM
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MY'14 W212 M276 3.5NA @60kMi
instructions published black on white ...

there's going to be denial involved at the Sce desk...


seal installation procedure

"best effort" is not enough: the procedure is almost clear and warns about leaks.
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Old 07-25-2022, 05:19 AM
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W204 C200, BMW E30 M3, 1980Gt Mini, Toyota Corona, KTM 200 EXC.
Hi are you sure it is not coming from the oil cooler matrix gaskets and leaking on to the stater motor and down to the sump plug area and bell housing?

My C200K needed new seal kit installed in to the oil cooler matrix, after installing the new shaped O-ring seals it is now 100% no leaks.

Last edited by NZ-Merc; 07-25-2022 at 05:22 AM.
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Old 07-25-2022, 05:21 AM
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W204 c250 cgi petrol facelift saloon
Originally Posted by NZ-Merc
Hi are you sure it is not coming from the oil cooler matrix gaskets and leaking on to the stater motor and down to the sump plug area?
Attached are pics of leak

Old 07-25-2022, 09:49 AM
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I don’t think these cars see RMS issues often. 190k miles and bone dry for our 2008 M272. You sure it’s not the tranny input shaft? Or a leak somewhere else and being blown back?
Old 07-25-2022, 09:52 AM
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Originally Posted by cvx5832
I don’t think these cars see RMS issues often. 190k miles and bone dry for our 2008 M272. You sure it’s not the tranny input shaft? Or a leak somewhere else and being blown back?
this is the m271 turbo charged engine, petrol. There is no oil present anywhere else, it is specifically that area pictured
Old 07-25-2022, 09:30 PM
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I’ve seen posts about the oil filter housing gasket leaking on the M271. It’s on the back of the engine, so if there is a possible leak that would transfer to the back side of the engine, that would be it. Barring that, the main seal is leaking again. In my experience, a reputable shop would stand by their work and make it right.
Old 07-26-2022, 01:41 AM
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Originally Posted by ash1212002
Attached are pics of leak
I see the photo, I was wondering if any higher up oil leaks or is it completely oil free higher up?

Last edited by NZ-Merc; 07-26-2022 at 01:43 AM. Reason: error

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