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1995 S420
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85 Posts
Discussion Starter #1
so last weekend i changed the oil in the transmission. i drained the fluid from the pan and torque converter. i dropped the pan and changed the filter. i installed the pan with a new gasket and tightened the bolts. filled her up with fluid. noticed this morning there is oil leaking from the transmission pan. a drop every 30 seconds or so. i went under there and tightened the bolts even more (thinking maybe they were too loose?). still dripping from the far rear left bolt. i didnt apply any sealant when i reinstalled the pan, should i have? i used redline d4 fluid (dex III), it took approx 8 quartz. any help would be appreciated, i will be looking at it again tomorrow. i hope i dont have to drain the fluid again...
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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6,543 Posts
If only from the sump then a new gasket is cheap and easy to replace, please note the sump bolts are only torqued to about 14nm max


Interesting post this, quite a few later 140's now leaking where the rubber boots that seal the interlocks are failing on the 722.6 box. Mine went and I know of 4 others all in the last 12 months.

Not a hard job, just drop the sump and the valve block and they can be replaced.
With this fault the fluid drips more from the bell housing, rather directly from the sump
 

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1997 S500V, 1999 S500 grand edition, 2006 s65 amg
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there is no need for sealant but i have been living with my tranny leak for 2 years lol if you had the 722.6 tranny i would have said the shift linkage bushing but i honestly don't know squat about the older transmissions
 

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1995 S420
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85 Posts
Discussion Starter #4
Didn't have any leaks until I changed the fluid. And I did put a new gasket when I reinstalled the pan. Going to check it again this morning, maybe adding some sealant wouldn't hurt. I don't want to over torque the bolts.. Sounds like I'm going to have to drain , drop, and refill again :/
 

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1995 S420
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85 Posts
Discussion Starter #6
i dont remember it having a washer, it was just a hex bolt. if it did have a washer, then i reused the old one. i dont think anyone has changed the fluid before, it has 83k miles on it, and the oil came out brown and smelling burnt. i can clearly see where the oil is seeping out of, its the rear most left mounting bolt for the pan. thats why i was thinking maybe hit it with some sealant, id rather not tighten it more than i already have.
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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3,886 Posts
Over tightening the bolts has been the cause of leaks, I woild take the pan off clean it and then lay it on a flat surface (glass) to see then re-install in a staggered fashion to the
14 lbs suggested torque.
 

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leaking pan

If you experience a leaking pan you are probably dealing with warpage. Quite often the original gasket should be reused, some transmissions say this on the pan. After 40 years working on this stuff I have found only a few good sealers for this. Something has changed and transmission oil will desolve most sealers we use. You can throw your gasket away and make one with right stuff sealer your auto supply will carry it. It is nasty stuff but will work fine. It is also expenseve and available in tubes or cheese grate type cans. cover it heavy and start all the bolts enough to start it to squish out and quit. Come back in a few hours and snug up the bolts don't overtighten. Please be sure you are not covering up any passeges in the pan rail as this will cause disaster. These are drain holes and must be left open. Over the years I have switched types of sealers several times and right stuff is now one of the best but I am sure there are others out there.
 

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1997 S500V, 1999 S500 grand edition, 2006 s65 amg
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Dropped the pan, cleaned, put on some sealant. Torqued to 14nm, filled her up... Still leaking.
my 97 does have a washer. also how sure are you that the leak is from the pan? mine i though it was the pan gasket and replaced over 3 of them and a lot of other stuff and it still has not cured my leak
 

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1995 S420
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85 Posts
Discussion Starter #11
i can physically see is seeping out between the pan and the gasket even tho i sealed it with "gasket maker" sealant. when i start the car, the leak stops. when i shut the car off, it leaks drop every 30 seconds. when im adding fluid thru the dipstick, it comes pouring out between the pan and the gasket. after messing with it for a few hours i gave up. i drained and filled and retorqed and cleaned. i still cant figure it out. the weird thing is, it wasnt leaking before i changed the fluid.. not a single drop. this isnt my first time doing a tranny service, but this has been the biggest headache for sure. i just thought it would be a good idea to put some fresh fluid in, since i know it probably hasnt been changed (and wasnt). now ive created a bigger headache. oh well, ill keep trying.
 

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1997 S500V, 1999 S500 grand edition, 2006 s65 amg
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i can physically see is seeping out between the pan and the gasket even tho i sealed it with "gasket maker" sealant. when i start the car, the leak stops. when i shut the car off, it leaks drop every 30 seconds. when im adding fluid thru the dipstick, it comes pouring out between the pan and the gasket. after messing with it for a few hours i gave up. i drained and filled and retorqed and cleaned. i still cant figure it out. the weird thing is, it wasnt leaking before i changed the fluid.. not a single drop. this isnt my first time doing a tranny service, but this has been the biggest headache for sure. i just thought it would be a good idea to put some fresh fluid in, since i know it probably hasnt been changed (and wasnt). now ive created a bigger headache. oh well, ill keep trying.
maybe it takes a while for the gasket to set? also i heard if the fluid is over filled it will leak too.
 

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1995 S 420, 2012 GLK 350 and 1997 Audi Cabrio; Previously 1982 280CE, 1974 450SL, 1974 911S Targa
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456 Posts
If only from the sump then a new gasket is cheap and easy to replace, please note the sump bolts are only torqued to about 14nm max


Interesting post this, quite a few later 140's now leaking where the rubber boots that seal the interlocks are failing on the 722.6 box. Mine went and I know of 4 others all in the last 12 months.

Not a hard job, just drop the sump and the valve block and they can be replaced.
With this fault the fluid drips more from the bell housing, rather directly from the sump
Try more like 7 to 8 nm...or 65-70 in-lbs. IN-LBS. NOT FT-LBS.!!! Use a 3/8" torque wrench...you can borrow one from AutoZone.

If you've overtightened it, you may have to replace the gasket and pan with a new one. A new pan is $47.50 at the dealer.
 

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1995 S 420, 2012 GLK 350 and 1997 Audi Cabrio; Previously 1982 280CE, 1974 450SL, 1974 911S Targa
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456 Posts
i filled it with approx 7.5-8 quartz when i did the fluid change. i might have overtorqed it when i first noticed that it was leaking. i guess its worth a shot to put a new pan / gasket
I'm gonna give you a pass on this one...GO BACK AND READ MY POST!!!!

YOU ARE OVERTORQUING THE FREAKIN' BOLTS!!!!

7 to 8 nm...NOT 14!!!

You have smashed the tabs on the pan and probably cut the gasket. Clean off all that liquid sealant sh!t, get a new pan and gasket and start over.
 

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1995 S320 SWB, 1997 S420 LWB
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192 Posts
Have you stripped the threads in the hole? Here in MN rust had eaten out my threads on my 95 S320, got new bolts from Ace Hardware for less than a dollar. Makes the job easier next time. I would advise you to use new bolts and if you have stripped the holes then re-tap them and use bigger bolts. As a rule of thumb always use new bolts. I wouldn't use any sealant anywhere near than transmission. You should be okay with the new gasket don't use the old one.
 

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1995 S 420, 2012 GLK 350 and 1997 Audi Cabrio; Previously 1982 280CE, 1974 450SL, 1974 911S Targa
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456 Posts
Have you stripped the threads in the hole? Here in MN rust had eaten out my threads on my 95 S320, got new bolts from Ace Hardware for less than a dollar. Makes the job easier next time. I would advise you to use new bolts and if you have stripped the holes then re-tap them and use bigger bolts. As a rule of thumb always use new bolts. I wouldn't use any sealant anywhere near than transmission. You should be okay with the new gasket don't use the old one.
Seriously, drcane? I grew up in MN and I never saw aluminum rust! They may have had a little corrosion, but a good shot of penetrating oil would have loosened those up for removal. If they galled and someone "gorilla-ed" them out, or they were severely overtorqued...then the aluminum threads could've been stripped out by the hardened steel bolts.

Guys...no finger-pointing here, I overtorqued mine the first time, thinking I could tighten them up by "feel". 65-70 in-lbs (7-8 nm) isn't much...use a 1/4" or 3/8" drive torque wrench!
 

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"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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7,642 Posts
ordered a new pan and gasket. will keep everyone posted.
Wishing you luck this time ItsCoo2PYoPants and dont forget to tighten those nuts in a hexagonal tightening sequenze .
This is why i dont touch the transmission ,it is not expensive to service it ,300 dollars does the trick ,by the time you buy the oil & the tools etc & the risk of doing it again plus the worry that comes after it ,no thanks ,transmission's are to delicate to play around with .
Good effort thou ItsCoo2PYoPants ,you got gutz to start this in the 1st place,i would'nt even think about it ,you should take pictures step by step for us here . :thumbsup:
 
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