W123 M110 : what does this part belong to ? - PeachParts Mercedes-Benz Forum

Jesper Bach · #1 02-24-2003, 10:37 AM

Just discovered a "dowel" protruding from the front right of the engine head.
There seems to be a "twin" just below it, firmly in place.

The dowel was halfway out, but I didn't dare pull it out all the way. Next trip, the same, just pushed it gently back into place, but what is it ?

Could it be placeholder for one of the chain guides
Neither the MB service CD, Haynes nor alt.auto.mercedes has given me any clues.
Will it be expensive and difficult to repair (probably) ?

Check the pics at w123.homepage.dk

Regards

Jesper

ctaylor738 · #2 02-24-2003, 11:09 AM

URGENT!

That is a a pin that holds the lower slide rail. I would clean it off, coat it with Loctite and drive it back in with a slide hammer and the right screw-in adapter (3mm?).

I think the large bolt is the plug for the oil pressure relief valve.

Jesper Bach · #3 02-24-2003, 12:36 PM

So i'm not in for at major repair here :p

The pin is not supposed to be locked to the slide rail by a locking-ring or so (internally) ?
If not, i take it, that the pin actually has a thread at the end and will screw onto the slide rail wthout problems ?
The 3mm screw-in adapter, would that be what is known in Danish, as a "bit", a suitable adapter, or what kind of tool are you referring to ?
Why did it come out in the first place - did the screw just come loose ?
Can my engine have been damaged by driving around with the pin halfway out, for i don't know how long ?

Thanks for the reply

Jesper

P.S. Nice looking 280 C You got Yourself there

ctaylor738 · #4 02-24-2003, 01:35 PM

You are in for a very major repair if the pin comes out and the slide rail falls down and gets caught in the crank sprocket! With the pin out like that there is only a tiny bit of the pin holding things together.

The pin does not screw into anything. It is driven into the block, through the slide rail, and into a hole on the other side or the rail. It is sort of a "press fit."

The outer end of the pin has a threaded hole, which you can see in one of the pictures. The impact puller/installer has a male threaded end which screws into the pin and then you user "hammer" part of the puller/installer to drive it in to the block.

You can use a hammer and a drift pin to drive it in, but don't damage the threads.

This is the only picture of the tool I could find.

Hope this helps

Jesper Bach · #5 02-24-2003, 02:02 PM

Well, the good part is, the guide rail cannot have fallen down as the engine idles nicely, although i only dared let it run for 20 secs Sunday, as i was pretty sure this could be(come) serious.
After looking closer at the exploded M110 drawing in my Haynes,
i can see that it clearly shows the guide rail (by name too).

But i'm not sure i can drive the pin in again, as it can be pushed just as far in by hand, as the pin just below it.
Maybe a good shot of Loctite wil help keeping it in place (hope the innermost end is not broken off) ?
Otherwise I will try to find a MB dealer who can fix it or maybe borrow/rent me the correct tool.

Thank You very much.

Jesper

Jesper Bach · #6 02-25-2003, 01:55 AM

Correction : actually Haynes calls this the "Intermediate gear guide".

Can it be changed with a new pin without risking the gear falls down and wrecks the intermediate gear

Jesper

ctaylor738 · #7 02-25-2003, 07:49 AM

That rail is held in by two pins so it's not going to fall off if the loose pin is removed and replaced.

What I think has happened, though, is that the pin has broken leaving the head in the hole in the block on the inside of the rail. I found an old pin from my 110 engine last night, and there is a groove about 5mm from the tip that would be a primo place for the break to occur. I think that the inside hole provides the real holding power for the pin.

Why don't you remove the pin for inspection and see if it has broken?

I am unsure of what advice to give you if this has happened. One difficult approach would be to try to drill the piece, insert an easy-out, and try to attach some sort of puller. Another would be to roughen or otherwise treat the surface of a new shortened pin, and install it with loctite and hope that the outer hole will hold it.

I guess I would try the second, on the theory that you could always try the first if it didn't work.

Jesper Bach · #8 02-25-2003, 11:00 AM

I was on the phone with my locall MB guy this morning and we came to about the same conclusion.

I wasn't sure if i did dare pull out the pin completely, because what if the guilde rail moves just 5mm's ? The pin cannot get back in.

If the pin indeed is broken "we have a problem".
Drilling a hole will be next to impossible, where would you find a 3-4mm drill more than 10 inches long, there will be drilling surplus (?) in the drive train, and can i find a 3mm pin strong enough to last the pull when the rest has to come out ?

I'm on my way to the shop for some Loctite (243 or 2701 seems to be the right type).

I'm on my way to the shop for some Loctite (243 or 2701 seems to be the right type), and then i'm going to take a look at the pin when i get home from work.

Thanks,
Jesper

Jesper Bach · #9 02-25-2003, 02:05 PM

The pin is back in place. I just need at test drive or 2, but it is only 2 degrees Celcius tonight, so it will have to wait until tomorrow.

Let me stress one thing : DO NOT take the pin out! It may never go back in (almost failed for me). Take it halfway out, wipe it off and glue/hammer it back in. Mine didn't take much force to go back in place.

I put a report on w123.homepage.dk if you would like to take a check.

Ctaylor, thanks so much.

Jesper

ctaylor738 · #10 02-25-2003, 02:06 PM

You will note that I said "difficult."

However, I was thinking. You could find the right diameter bolt - 6 mm? in the right length, and file most of the threads off, leaving 5-6 mm of threads near the head. Then you could tap the hole, insert your new pin and tighten it with a wrench (and Loctite).

You might even be able to find a specialty bolt like this.

Jesper Bach · #11 02-25-2003, 02:17 PM

Actually it was not difficult at all, but i (felt i) had the need to know if the pin was broken, so i took it out - it was not!

As luck have it, i have a 5mm mandrel i use for the brake pins, it fit exactly inside the thread, so i didn't need to put in a M6 screw (probably the cheapest and most useful tool i have bought so far). Just enough space for little nudges with my smallest hammer, and when the pin was almost in, i used the hammer as a lever and got the pin 2mm's extra in.
I actually asked my local MB shop, and they said "we just use a hammer".

As a Danish saying goes : In the land of hindsight, we shall all
kings

Jesper