103 Front Cover Leak- Where exactly?
 

Got oil?

Front Cover Leak:

Front cover has been leaking oil somewhat since I have had the car. Not so much, but messy nonetheless. Obviously a very common problem based upon posts...

But where exactly is the source of the leak?

In the diagram below, is the problem child #143 (Cam Gear Cover Gasket) or #142 (Cam Gear Cover Seal)

Or both for good measure? Neither? Am I even barking up the right tree? :confused:


Extra credit question:
Is part #139 (Distributor Rotor Bracket) a 'wear' item? Hate to reinstall marginal parts because replacements are not in hand...

TIA for any help.

I see yours is an M103. You want to replace #143, the cam gear cover gasket. ;)

Untrained eyes mistakenly associate this type of leak to a faulty head gasket...

The front cover is a tricky beast to seal. Getting part 143 (horseshoe gasket) in place properly is most but not all of the battle. The rest is using and applying the proper sealant. Check the archives.

Part 142 is just a seal but you might as well replace it when replacing part 143. In fact I'm from the camp that says to put part 143 in place then fit part 142, as opposed to the manual that says to fit part 142 into the front cover first. The front cover has to come in at an angle to keep part 143 in place so there's a chance to nick part 142. At least that the easy way to get the front cover in place.

I think part 139 is noted as a replacement item because if it takes a set on the cam, you can damage it when removing it.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

M103 front oil leak
 

Mine's also been leaking from the front for quite a while. Replaced 142 and 143 a couple of times (my tech did it) and it still leaks, although less now. The second time they did it, the leaking slowed quite a bit. What I have since found out is that it is also leaking from the head gasket slightly. Most of the leaking was from the camshaft cover (from 142 and 143), but some is from the head gasket at the passenger side front corner of the block. Fun, fun, fun.

A member here has a good quote under their username - "If it's German, it leaks". Seems to be true. :rolleyes:

Thanks for the help!

Glad to hear it is not generally the LOWER cover that leaks.

Now that would suck...

I just completed this job in July. It was very easy to do. You must use the proper sealant (loctite 5900?) from the MB dealer or Fastlane. Make sure you put enough in the corners between # 143 and the head. Replace #142 while you are at it. I also replaced the vave cover gasket for good measure. The most expensive part is the sealant

My car is now bone dry for the first time in years.

Ed C.

88 300TE

csnow,

Where are you getting the diagrams you use in your posts? I own 3 different W124 manuals and the Service CD's and I haven't seen these diagrams in any of them.

Thanks,

Gary

diagram
 

I was able to get a diagram from the catalogue I got from Performance Products. Just visit www.************************ and request a catalogue once you've specified your car. It has what you're looking for and more.

If anyone else have a diff source that'll be nice... :)

late,

Yes, no offense to our sponsor, but I do find the online performance products diagrams very helpful in discussions here.
Actually, their old site was even better, since it had an exact copy of the drawings in their catalog, covering more items. Old site was slow and unreliable though.

The service CDs in particular have awful drawings. No context at all. I swear MB just likes to leave us in the dark. The most useful manual I have for the 300E is actually a 'Parts Identification Manual'. Nothing but drawings (not even a brief description for each part) , but at least you can see how bits go together. Also you can fax (or scan) a copy of a page to Phil so that he knows what the hell you are talking about.

I recently rebuilt my manual shifter mechanism, and there was absolutely NO WAY I could have done it without this book as a guide! Best $40 I have spent on my MB.


Link to "1986-89 124 Parts Identification Manual" at books4cars.com

Do you have any way to post a representative image from the Parts ID Manual so we can get an idea of the quality of the diagrams?

Gary

Sure. Quality is actually better on paper, since I had to drop resolution to post.

More. This page did not lose so much in the conversion. Actually, to give proper credit, Phil converted this one.

nice pics
 

Now those are diagrams. Looking at drawings all day (P&IDs), one can surely appreciate this kind of quality. Time to buy a book...

The shifter parts page might be a screen shot of the EPC. Why would Phil use a hardcopy resource?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

csnow wrote:

"Nothing but drawings (not even a brief description for each part) , but at least you can see how bits go together."

Then the item numbers don't refer to anything in the book at all?
Any idea if these drawings were taken from an old parts fiche, with the part number/descriptions left out?

Gary

Dunno anything about Phil's ways.

My paper page for the 5-speed looks identical to that one from Phil, except that the numbers have changed since my 1986 copyright date.
I have seen a microfiche version of this book somewhere as well. That is what most dealers used to use in the 'old days'.
Maybe it was intended to be used with a second book for cross-reference. If you look at the first (poor) image, there are numbers on the left and 'group' numbers on the top. I assume these have some meaning, but not to me. I would like to know.

Has been difficult for me to make these particular scanned images both pretty and smaller than 60k for posting. I'm sure there is a way. Phil's picture is just 23k.

I need to do this as well to my '87. The leak is staring to get much worse. I don't have a manual....could anyone forward the instructions for replacing the mentioned parts #142 and #143? Thanks in advance.

I did our 91 300e cover several months ago and it was actually a pretty easy job. Here is a link to a posting regarding this: 103 Front Cover Seal

Be sure to follow the links as well. Good advice by Larry Bible and others.

Additonally, here is a group of suggestions (sorry, kinda of long) with advice I collected before doing it:



Replacing 124 Upper Cover Seal

It is no big deal to replace this seal by removing the upper cover if you know the key.

1. Get the recommended sealer from MB. It will let you slide the cover rearward without disturbing the lower U Seal gasket.
2. Put the cam seal in the cover on the bench, and then oil the seal. While sliding the cover rearward use your fingernail to see that the seal is starting over the shaft smoothly.
3. Push the cover rearward into place and bolt in place.
4. Gob the sealer in the lower rear corners, and of course, use it on the U Seal and rear sealing surface.

Nothing to it if you're using the right stuff.

Part number for this stuff? the manual seems to indicate one type of sealant for the corners and another part number for the metal to metal seal? Your suggestions is to place the sealer on all contact surfaces. so put the sealer on top of the rubber "U" gasket as well as in the corners and on the metal mating surfaces?

Is your leak at the top timing cover or the bottom timing cover? The top timing cover is no big deal as long as you use a "slick before cured" sealant on the bottom u-seal so that the cover while slide rearward into place without disturbing the u-seal.

The M103 has a ratcheting tensioner and is probably the most durable timing chain system on any of the MB's. However, the chain is cheap and since you will have the cover off for access, it wouldn't be a problem to roll in a new chain. If you do, remove the tensioner mechanism, it will require some odd size Allens. Once removed, push the plunger all the way out of the ratcheting mechanism, and reinsert from the back. If you do not take this tension off, you will break something.

I'm with Larry on this as far as the tendency for 103's to leak mainly from the front cover lip seal. My experience has been that the 103 rarely has a external oil leak from the head gasket itself. A failed head gasket on a 103 almost always is an internal leak from oil pressure into the cooling system, gives you the appealing "butterscotch in my coolant tank" effect.

On the actual repair, i have to disagree (if I understand his recommendation correctly) with the repair recommendation.

When reinstalling the lip seal (the U shaped seal Larry mentioned) only a thin film of oil is applied to the top of the lip seal. The ONLY sealant to use on this job is Loctite 5900, it's applied to the mating surface between the front cover and head (on the cover) and also prior to installing the lip seal a dab of 5900 is applied to the back of each side of the groove on the lower cover (the groove the lip seal squeezes into).

The 104's also leak from the front cover lip seal, but also from the right front corner of the head gasket (hard to tell between a front cover leak and a right front head gasket leak) and also the 104's will leak from the right rear corner of the head gasket. I've never seen a 104 mixing oil into the coolant like a 103 or a 102.

Knowing lots of M103/102 owners, and being an ex-M103/102 owner myself, I would comment that they have a lower incidence of head gasket failure than the M104 engine.

However, the front cover is quite failure prone. Follow Gilly's advice on that repair, and it'll last much longer than it did from the factory.

I've seen some M103 engines with leaking main seals, front and rear. On further inspection, found severly-overfilled crankcases.

Overall, I wouldn't characterize the M103 engine as a "leaker." Sure, they can, and do, but I think overall the 103 is pretty good.

The tool for the seal that Michael correctly told you that you don't need, is substituted for by using a fingernail around the seal as you push the upper timing cover rearward into place. You are seeing that the seal does not "fold".

The importance of following the tensioner instructions cannot be overstressed. If you do not, you can break something expensive because you will be putting it back together with tension. Push the ratcheting plunger all the way through after removing the tensioner assembly, then start it from the outside, don't push it any further than just starting it into place. Upon startup, oil pressure will ratchet it into place.

You can do it either way, but I left the injection system in place, rather than pulling it off with the head. It worked very well for me, I had to remove and replace a few of the manifold bolts from underneath, but it was no problem. It was preferable for me to prevent ruining some of the vacuum and electrical connections on the injection system.

Use the sealant that Michael mentioned on the upper timing cover. It is slick and allows you to push the timing cover rearward without disturbing the USeal below the cover.


A new cam seal should not leak unless:

1) It is not seated correctly.
2) The cam has worn the head (no bearings) surface down enough that the cam is lower and thus does not line up with the center of the seal. It would leak at the top.

I replaced a seal that I installed with another when I did not seat it correctly.

I also noticed that the cam was closer to the bottom of the seal than the top. But not enough that the top leaked.

I dug out the seal, cleaned the surface of the cover and inserted another seal. (oiled on the inside) I tapped it into place using a tack hammer until the seal was even with the surface of the cover. No leak now.

I just resealed the upper timing cover and replaced the cam seal on my '88 260E. I installed the seal in the cover first, but it was difficult lining up the cam seal and the timing cover on the studs and it is easy to damage the seal while installing the cover.

Mine turned out okay and the timing cover is as dry as a bone but if I had to do it again, I would install the seal after the cover is in place. Use a block of wood to drive it flush with the face of the timing cover. I also used some 600 grit sandpaper to smooth the end of the camshaft so it wouldn't cut the new seal (it was very sharp).


Haasman

Wow Haasman, Thanks for the detailed reply.