I just don't get it.

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JohnDavies

Active Member
Joined
Feb 28, 2017
Messages
131
Location
Ripon, N. Yorkshire
Car
ML270cdti & C200 Coupe
Today will be the 5th time i have tried to seal my auto gearbox sump pan in the same amount of weeks.
After changing the oil/filter and thoroughly cleaning the box i line the sump pan edge with sealant, set in the new gasket and sealed the top of the gasket with sealant and refitted the pan to the box. After a couple of days i noticed an oil drip on the ground. Yup, it was weeping from the gearbox sump pan. I have now repeated this operation 3 times without success so i purchased a brand new sump pan from MB thinking that the original may have had some distortion. STILL leaking, so today will be my 5th attempt if this fails then i just will not know what to do.
Am i doing something wrong?
I am using gasket sealant, is this right?

Heeeeeeeeeeelp.
 
You dont need sealent on a 5g Box. The Gasket is the Seal Buy a New Genuine gasket, Torque the Bolts that retain the pan to 8nms.
 
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The first time i refitted the sump i did not use any sealant as i believed in exactly what you say, that the gasget is the seal but it leaked so it was on the 2nd and consequent attempts i used sealant. I will try again and torque as you suggest without using sealant, fingers crossed and thanks for your very welcome input.
 
Is the filter clipped in properly?
When mine didn't locate properly, the sump wouldn't fit.
Bit obvious, I know but...
 
When you refitted, did you use a new gasket?

It's like a copper crush washer, it's a one time use thing. The first crush seals, it's then ruined for any later re-tightenings.
 
Yes i have used a new MB gasket every time as well as using new oil, costing a small fortune. Having another go this evening and will be my 5th and final attempt. If it still leaks then i shall have to get it into an MB repair shop as it will have defeated me.
 
the trick is a new gasket and dont over tighten the bolts - they barely need any pressure at all. If you over tighten you warp the sump and it leaks.
 
You have to do this with a torque wrench, 8nm is barely more than finger tight, and do them up using opposing bolts if you know what I mean.

Been there and done the same as you
 
When you refitted, did you use a new gasket?

It's like a copper crush washer, it's a one time use thing. The first crush seals, it's then ruined for any later re-tightenings.

Not correct, IME.
Whilst a new one should of course be used, one will usually see NO damage or deterioration to the old one's flexibility or sealing surface.

They do not 'crush' like some seals. They are not compressed much at all, at the low torque of 7 Nm.

I suspect some crud is at play here...
 
There's a torque pattern you need to follow too so the gasket is compressed evenly.
 
Not correct, IME.

Are you familiar with similes? My parallel was that it's a one time use thing. :thumb:

I know a gasket doesn't 'crush' like a copper washer, but any imperfection in the surface is imprinted in the gasket and if it doesn't marry up perfectly the next time you've a channel through which it'll leak. That's why a new gasket is supposed to be used every time.

As a new gasket has been used, then I agree, it seems overtightening has happened causing the leak.
 
Take it to an Indy.
 
Torque pattern, this may not be your gearbox but it gives general idea of sequence.


208148d1303382633-those-who-have-flushed-their-trans-trans_pan_torque.jpg
 
I would think a set of new bolts may be a good idea given the number of times the pan has been off, mine cost me about £8.00
The only way to do a fluid change is new filter, gasket, bolts and pilot bush, I used about 12 litres of fluid to flush the TC. No leaks no problems, level checked with dipstick.
 
Job done (again) new gasket fitted and torqued to 8nms as advised in replies. Left engine running for an hour this morning and completely dry now. I will now run the car for about a week then get underneath to check for leaks if none are apparent on the ground. Hopefully it will remain leak free. I will not mark this thread as 'solved' but will leave it open for the next week or two just to make sure. Many thanks for all you guys that gave your input and advice.Confirms just what a great club this is.
 
£500 later and a £22 fix

5 times i have changed my auto gearbox sump gasket without success as still getting a leak. Upon deepening my search, as i could not believed it still leaked, i have eventually found the leak source. It was never the gasket that was leaking, it was the plastic plug at the front of the gearbox just above the sump that carries the wiring loom into the gearbox. This has been the problem all along. Mercedes have also informed me today that apparently this is a common problem on MLs and as such they carry them in stock.
This has been a very expensive lesson for me and has taught me that what you see may NOT be what you are getting.
I hope that this post may help others out there who assume they have a leaking gearbox sump seal on their ML.
 
Thanks to you I will now know what to look out for. You should console yourself -imagine if you had been paying someone to do what you did.
 

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