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6.9 rear engine seal DIY?

Started by Jan S, 26 May 2022, 05:18 PM

Jan S

Car: US 1975 116.032 450 SE
Engine: US 1977 M100.985 6.9 (not original)
Transmission: 722.004 (the transmission for the original car, i.e. the 4.5 liter)

I'm slowly getting tired of the oil leakages under the car. I probably need to do something, not sure what and what it requires.

See pic, leakage after 20 hours. Yesterday it was twice the amount. It comes out directly under the torque converter.

It's engine oil, so I guess It must be the rear seal on the engine, see second pic and part 109.

A few questions I am asking myself:

- what do you think, am I right?
- probably not critical for the engine?
- replacing the rear seal, is it a DIY job? I have not done this before ...
- When replacing the rear seal, should I also replace the front and rear transmission gaskets?
- other things I should do when the transmission is out?

Advice and comments highly appreciated.
1975-mod W116 450 SE with 6.9 engine

Randys01

I have to same problem. :'( .but I suspect the crank has to come out.

rumb

https://cdn.w116.org/tech/Manual_100-985_Mechanical_04_82.pdf

pg 62 replace rear radial seal

This is a pull the engine job. You cant remove the crank without removing the pistons, so this is a big job. 
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

raueda1

Quote from: rumb on 26 May 2022, 07:38 PMhttps://cdn.w116.org/tech/Manual_100-985_Mechanical_04_82.pdf

pg 62 replace rear radial seal

This is a pull the engine job. You cant remove the crank without removing the pistons, so this is a big job
LOL, don't sell it short Robert, this is a HUGE job ;D . My car has a similar leak.  It would be interesting to know how many of these cars don't leak if they haven't been rebuilt at some point.  Oddly, I find that the more I drive the car the less it leaks, so there's that. 

Anyway, at the end of the day you're really looking at either rebuilding the engine or suffering from eternal anxiety from having it apart and not replacing things.  After pulling off the top end, heads, pistons and all the crank you're probably going to want to replace the bearings and a lot of other stuff.  I came very close a couple years ago while replacing a bent rod and rod bearings.  In the end I just couldn't muster the will to pull the crank.  That was probably a mistake but I just couldn't stand the idea of having all apart and not measuring journals, searching for bearings etc.   Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

I'm probably being dense here, but why can you not just pick the seal out and drive a new one in with a suitably sized pipe over the end of the crank?
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

Thanks to all of you for valuable comments/advice!

I initially thought this was a seal that could be pushed in - in axial direction. But no - it must be pushed in in  radial direction, with crank out ... as several of you mentioned. See attached pic from service manual.

Sounds as a BIG job, indeed. Another candidate on my to-do list ...
 
1975-mod W116 450 SE with 6.9 engine

Jan S

Attachment
1975-mod W116 450 SE with 6.9 engine

daantjie

Ah yes indeed, I thought my idea was too easy 8)
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

Quote from: daantjie on 06 June 2022, 02:42 PMAh yes indeed, I thought my idea was too easy 8)

daantjie, I believe the front seal can be replaced using your suggested method, If I remember correctly.
1975-mod W116 450 SE with 6.9 engine

daantjie

Still trying to give you some hope here ;D

Maybe it is the torque converter seal leaking rather?  If I look at the EPC, the part number is 0049970547.  But then again you would likely be seeing ATF as the leak and not engine oil..?
Daniel
1977 450 SEL 6.9 - Astralsilber

gurrier

A stop gap option - but have you considered additives.  Liqui Moly, (IMO a reputable company) market Motor Oil Saver that the technical blurb says "As automotive rubber ages it loses its elasticity through oxidation of its nitrile backbone. Motor Oil saver is a blend of esters that work to replace the lost nitrile groups"  I have used it to good effect previously - takes a while to work.
1973 350SE