Mystery oil weep from rear of engine...

[RaceDiagnostics]

I've had the leak for the last 4 years since I did the engine rebuild, but it's never been bad enough to do anything about it. It's coming from either the main seal or the cover it's fitted to. Either way the transmission needs to come off for to check and fix.

It looked like this during the rebuild.

The question is will I be able to get the trans out with my style of scissor lift. So far I've been totally satisfied with it is I've had to do lots of sill work on the cars, but will the cross member make it a non starter. Time to find out.

 

[RaceDiagnostics]

All looks good.

Access to the trans is well ahead of the cross member.

Exhaust and downpipes will need to come off first unfortunately.

Busy the next couple of days, just ordered a new rear seal so looking forwards to getting this job done finally towards the middle of the week.

 

[Nederlands]

Did you use silicon gasket?
(Blue stuff)

 

[RaceDiagnostics]

I used Holymar Blue which was called for in the Mercedes repair manual, I now wish I'd used something more modern like locktite 5980.

 

[colnerov]

There's nothing wrong with Hylomar Blue. Only the way you spell it.

 

[harveyp6]

There's nothing wrong with Hylomar Blue. Only the way you spell it.

He's using all the right letters, just not necessarily in the right order........

RIP Eric Morecambe.

 

[Nederlands]

Great that mercedes called that.

I've got bad experience with silicon gasket allot.

I would use loctite 5923

A side note,
I use to work on old English (pre ww2)cars
And the 5923 always did it's job

 

[Farside]

I used Holymar Blue which was called for in the Mercedes repair manual, I now wish I'd used something more modern like locktite 5980.

Hylomar Blue still works perfectly well.

 

[jo1010]

Idk but on the 300tdi land rovers with that kind of seal rtv is always used ..I suspect because of the dissimilar metals in seal carrier and block....

 

[Ubique]

What engine is it? a lot of M-B's have the holes tapped for the flexplate as through holes, the bolts should be replaced each time as they are pre-loaded with sealant. I have also seen crankshaft radial seals leak due to not being exactly aligned with the 'wear line' on the crank, other manufacturers also use different setting tools depending upon how many times the seal has been replaced to ensure the new seal runs on a virgin bit of crank.
Assuming it's not an OM651 (it doesn't look like it from the limited view), are there any oilways behind the flexplate (or as in the case of OM651) above it, that may be leaking into the bellhousing and giving the appearance of being a rear crankshaft seal or mounting plate?
Other than that, I can't really help with M-B stuff prior to 2010-ish.

 

[RaceDiagnostics]

It's a 117.985 4.5l, pretty sure all the bolt holes in the crank and block are blind, but I will be checking. I did find someone saying that the cover plate bolts holes may go into an oil gallery but doubt that. The seal in there just now is a repair size to avoid the groove in the crank. I do plan to sleeve the crank anyway just in case it has a nick on it.

 

[8ob]

The seal looks distorted in the housing, was it pressed in with the correct size mandrel or twatted in with a hammer?

Bob

 

[Bobtail4x4]

before you get too far into it, check the breathing on the engine,
too much pressure etc etc

 

[RaceDiagnostics]

The seal looks distorted in the housing, was it pressed in with the correct size mandrel or twatted in with a hammer?

Bob

No mandrels round here, plan to lathe one up if needed this time.

 

[Ton-up]

Could you get one of those small endoscope cameras up there . Could be the rear of the sump gasket. Also, Are they oil gallery plugs above that could leak?

 

[RaceDiagnostics]

Could be any of these, but no way to get an inspection camera up there.

 

[Trevorleach]

I used Holymar Blue which was called for in the Mercedes repair manual, I now wish I'd used something more modern like locktite 5980.

I think some of the silicone adhesives are to squishy if that is the correct term! and Blue Hylomar is excellent stuff.

 

[8ob]

No mandrels round here, plan to lathe one up if needed this time.

You can get away with sockets/tube and a hammer or vice on the smaller seals, all to easy to deform the bigger ones. For the time it takes I always knock up a seal driver on the lathe, I always include a recess for the lip as well. Getting wrong is too expensive and time consuming.

These truck hub seals are both expensive and fragile, I spun up a seal driver that registered on/through the hub bearing lands,pushed them in dead square, worked a treat.

Bob

 

[RaceDiagnostics]

Was planning on doing a bit of prep work today and remembered that my little scissor lift was at the back of the shed, and I'd just put away all the garden furniture.

So everything back out.

Then took my mum for a quick hospital appointment and just got home 5 hours later. Everything still laying outside. Don't think I'll have any distractions tomorrow.

 

[Ubique]

I think some of the silicone adhesives are to squishy if that is the correct term! and Blue Hylomar is excellent stuff.

You have to be careful with sealant bead size, too much will actually make the joint more prone to failing due to torque relaxation of the fasteners as the temperature change affects the sealant. Generally a sealant bead of 1-2mm is all that is specified, having a correct size sealant applicator gun helps achieve the correct bead and placement (as does warming it in hot water prior to use) rather than the push-stick supplied.
Hylomar - red or blue, has a much higher viscosity than most silicone based sealants. Red is generally similar to Loctite 5999 which is designed to be used on differentials etc. whereas blue is roughly equivalent to Ford WSS-M4G323-A10 in performance, but not composition. Anerobic sealant is good for machined surfaces (i.e. not pressed covers / sump pans) my favourite is Ford WSK-M2G348-A5

This is a good web page to find the best sealant for your application - gone are the days of 'just use ...... it'll do' https://www.msds.ford.com/cpc/productGroups.asp?pgn=1