clutch wear feeler gauge - PeachParts Mercedes-Benz Forum

samboyellowsub · #1 04-26-2010, 08:25 PM

the clutch wear indicator for the 123 manual transmissions is mentioned about 10 times that i can find but I can't find a post that describes how to use it.
I don't have the gauge, but my slave cylinder is out (new one comes wednesday) and if it were installed, and i inserted the gauge, the gauge would bottom out. in other words, the notches would not be showing.

when i'm just holding the end of the plunger up against the back of the throw-out bearing lever, the thicker part of the plunger is all the way in the hole (the back side of the thick part of the plunger is about a 1/2 inch deep in the hole).
Does this mean I have a 1/2 inch of good clutch left, or is my clutch 1/2 inch beyond its wear limit (which doesn't seem possible to me)?

thanks

aaa · #2 04-26-2010, 08:39 PM

I don't think the "guage" measures anything, it's an on/off thing. Either it slides in or it doesn't. If you look at the slave cylinder rod you'll see it has a "notch" (there's a better word...) on it, it doesn't slowly taper or anything.

samboyellowsub · #3 04-26-2010, 08:47 PM

i know it's an on off thing.

what is on and what is off?

in other words, what is good and what is bad

samboyellowsub · #4 04-26-2010, 09:14 PM

does anyone know?

aaa · #5 04-26-2010, 09:27 PM

Well since I don't have a manual on me right now (I remember reading it a some point somewhere but have forgotten now), I'll think about it logically. The thicker the clutch is, the farther forward the fingers of the pressure plate will be. So the opposite would be the case for a thinner clutch, farther backwards, along with the release bearing and fork being farther backwards.

So the "notch" is just the front two inches or so of the slave rod being of a thicker diameter, and the back portion being a thinner diameter. The tool slides over the thinner part, and won't slide over the thicker part. Eventually the clutch gets thin enough to push the rod back far enough for the thicker part to be the exposed part in front of the slot for the tool. So when you can't slide the tool in it's worn.

samboyellowsub · #6 04-26-2010, 09:40 PM

thank you, i needed a second opinion, i thought it should just be a logical but i couldn't remember where the pivot point was on the fork so i didn't know if it was the obvious answer or the opposite of the obvious answer

. so thats not so bad - i have over a half inch of usable clutch thickness until the thicker part is flush with the hole.

thanks for the help

aaa · #7 04-27-2010, 02:28 AM

Are new clutches even 1/2 an inch thick? They're less than a 1cm iirc.

samboyellowsub · #8 04-28-2010, 01:08 AM

well, i took the plunger and the thick part goes in about a 1/2 inch past the point where it is flush with the transmission housing

#9 04-28-2010, 07:19 AM

The dimensions for making the gauge are in a Haynes manual. It's quite easy to make one out of a piece of sheet metal, beer can or anything that's lieing around. Don't try to measure the length of anything, just make the gauge. It's worth having in your tool box. It's one of the most clever things I've ever seen. Those guys in Stuttgart are pretty clever.

samboyellowsub · #10 04-28-2010, 02:08 PM

Larry, since i have the old slave cylinder out and it is dismantled anyway, i decided it was appropriate to take the plunger and actually see how much longer until the thicker part of the plunger would be revealed

samboyellowsub · #11 04-28-2010, 08:30 PM

Well, I got the new slave cylinder in, bled it, cleaned up in under an hour and a half with only the front tires 3 inches off the pavement (tight quarters). The clutch is solid as ever.
I don't know what everyone's fuss is about bleeding the clutch system. I left the two bolts loose enough to fit a wedge on the underside to cock the SC up a bit. Just gravity feed it real fast, wait for no bubbles, close the bleeder valve. Tap on the SC with a wrench and gravity feed it again. I've never had any "soft clutch" problems doing it this way.

I torqued the bolts to 14 foot pounds though, is that too much? I was going by a generic torque guide in the manual.

#12 04-29-2010, 07:13 AM

Yes, the first time I ever messed with one of these clutch hydraulic systems, tried several things. Over the years I learned if you just do a quick two man bleed job and let it set overnight, the rest of the bubbles will work their way to the reservoir. At least enough of them for it to work properly.

Clutch bleeding on a 124 car is a different issue, however.