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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
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Discussion Starter · #1 ·
So the upper timing cover has always been a source of oil leaks, here’s mine on the M103, last summer installed new bottom seal, adding a little Hylomar sealer usually helps stops the leak
Today I noticed the bolt hole on head has a slight indent and the corresponding bolt hole on cover is larger then the other ones?? Is there something missing? Why would they do that? Could this contribute to oil leak?
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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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I haven't had that off a car in a very long while. There are however, some bolts on the front timing cover that require an O-ring in a groove that's hard to see unless you look for it.

One member took me to task over this until he was shown a pic of the groove. Even the bolt had a very smooth shoulder for seating inside the O-ring.

Kevin
 

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W163 and General M Gremlin
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Check the epc on your engine.
M103.9xx?
I recall seeing a small seal ring on one, awhile back. Or was that on the timing case?
Not sure on the M104s (haven't done one of these)
 

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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
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Discussion Starter · #4 ·
I looked at EPC and doesn't show any O ring just a bolt, its just so strange the case hole is so much bigger than other 3.
I was thinking maybe oil flows thru it somehow and contributes to the oil leak on that side, I know the bottom seal supposed to do that job.
 

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Discussion Starter · #5 ·
The only thing I can think of they did this so cover mates perfectly to cylinder head, guide pin also helps.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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I looked at EPC and doesn't show any O ring just a bolt, its just so strange the case hole is so much bigger than other 3.
I was thinking maybe oil flows thru it somehow and contributes to the oil leak on that side, I know the bottom seal supposed to do that job.
And it won't show it....you have to look for the groove in the housing for it.

Kevin
 

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Not gonna show it that I've ever seen. You have to look for the groove in the housing and the bolt with the smooth shoulder sized for the O-ring.

Classic case of what's on paper versus real world. I'm not saying that's THE bolt with the companion O-ring....I'm saying I don't remember. But it's a simple matter of finding the groove in the housing. Plus, when you pull THE bolt out, there's oil on the threads.

I got into this with plinker once....showed the location of the bolt. He maintained it wasn't in the EPC. I assured him I'd just done it with the O-ring and bolt. Then another member stepped forward and actually showed the groove close up without the O-ring yet. Never got any acknowledgement from plinker.

It's analogous to doing something and then someone telling you, you didn't. That's fine if you live in The Theater of The Absurd, but I don't.

Kevin
 

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Discussion Starter · #9 ·
Ok this is weird has heck! check this out that left bottom hole I can sick a 6 inch dowel all the way in without bottoming out, goes inside of head, all other holes for cover I can see the bottom of hole, I may find a small O ring for that indent.
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Discussion Starter · #10 ·
Maybe the machinist was smoking something really good and said whoops, no one will notice.
 

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Discussion Starter · #11 ·
I checked on eBay and there's about 4 used ones for sale, same as my 92, 86 to 93 W124s have the mystery hole.
 

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IIRC, there is a O ring that goes in the hole that meets up with the upper right bolt hole on the fan clutch bearing bracket.
 

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Lol....if you pulled the bolt out and it had oil, it needs a O-ring seal. I can't tell from your pic what's going on in there but it looks like threads? In that case, maybe the machinist was smoking something.

Other than those false threads, is there a distinctive groove in there for an O-ring? If so and it's well formed, you don't have to worry about the false threads.

Who knows, maybe a PO tried to force a large bolts through that holes.:oops:

Kevin
 

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Discussion Starter · #16 ·
Oh by the way all bolts are the same for upper case,
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Third from the top looks like it's possibly shouldered. Mic it.

Kevin
 

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Discussion Starter · #18 ·
Mic all the same, I guess oil could find its way from head thru bolt threads and cause a small leak at lower case cover, I’m just going to put sealant on threads.
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Actually the leak can be substantial. Not as in sump draining, but messy. Once these engines get some real age on them, they can leak like the old English sport cars.

Kevin
 

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What I can't figure out is what they were trying to accomplish with that over-bored channel. If you look closely its not even round. Is it possible that hole bisects an oil return galley?

If you inserted a hose tightly into the hole with a funnel on the end, if you filled it with oil would it drain down?
 
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