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1976 450SL
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629 Posts
Discussion Starter · #1 ·
I'm replacing my valve stem oil seals, and see this on two of the valves guides

It looks like the 'groove' that the seal fits into has been worn, as if the seal was moving up and down with the valve. The valve guides themselves do NOT seem to be moving (they didn't shift at all when I pulled the old, hardended seals off - and I had to pull hard. It's also worth noting that the seal itself didn't seem to be moving, but clearly there is some wear here.

One of these cylinders appears to be burning oil (based on the plug), but the other plug looks pretty good (and just like the others)

Anyone seen this before?

2690299


2690300
 

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1979 450SL UK spec
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2,222 Posts
It does look like a wide grove, I still have the 16 guides I took out last year, I will have a look at this and post up a picture.
 

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Premium Member
1976 450SL
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629 Posts
Discussion Starter · #3 ·
It does look like a wide grove, I still have the 16 guides I took out last year, I will have a look at this and post up a picture.
Thanks

Also - do you know if the old seals were ever soft? Mine are baked like bakelite. They are (were) whitish color, with coil springs around each end.

Wondering whether replacing them is going to fix my smoke issue. I have checked a few of the bores with my endoscope (including the one where the badly oiled plug was) and the bores and pistons look really good - there's lots of cross-hatching still visible on the bores, which amazes me after 250k miles (I do wonder if it was rebuilt). Also, as mentioned, none of the guides (so far) appear to be loose (3 more valves to go though!)

I notice that the underside of the valves (i.e. the part you see looking up in the combustion chamber) all look pretty black/oily/carbonized).

-Steve
 

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1979 450SL UK spec
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The seals I removed a couple of years ago were also white with a spring, so maybe OEM.

Like these.

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Here are some pics of the ones from my engine.

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They were solid when they came off.

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Here are the exhaust valve guides. all look OK.



And the inlet guides, looks like copper, look at 5th from the left.



Close up, deffinite wear from a moving seal.



But what are the consequences??????????
 

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1976 450SL
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629 Posts
Discussion Starter · #5 ·
Close up, deffinite wear from a moving seal.



But what are the consequences??????????
Thanks for posting those. My seals look a lot worse than yours...

Yes - that's what two of my guides look like (though I think they're slightly worse - the wear is more defined). Do you know if this was the same guide that was loose?

I'm also assuming that (if loose) it came out really easily - when you pulled on the seal?

-Steve
 

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1979 450SL UK spec
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No, the loose one was the one on the far right, you can see where I roughened the surface which was subsequently worn smooth again. It lasted only 1000 miles or so befor coming loose again.
 
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