I have a 1979 model W123 230 Mercedes-Benz and what happened was the clutch went down but doesn't want to come up. Anyone got any ideas on what could be the problem.??? I have already checked the clutch slave cylinder and it seems fine.

Does the system have fluid? Is there fluid leaking from the master cylinder? How did you "check" the slave cylinder?

I have replaced a clutch before when it didn't need it because I was convinced that the hydraulics were okay. I have also had a finger break off on a pressure plate that caused weird problem, but that is certainly not a typical failure.

If the pedal goes down and won't come up, I say the odds 98 out of a 100 that the problem is hydraulic related.

Good luck,

I agree with Larry; high probability of hydraulic problem.

The problem will be that the column of fluid between the master and slave cylinders has been shortened. Bleeding is what is necessary, but the master cylinder is often the problem. Bleeding only extends the column of fluid if all cylinders are sprung to their realesed state. There are some cars that are always problems the MB isn't one in that year (the old 110 chassis was hard).

There are bleeding devices that improve results. One such method is to pressure bleed in the reverse direction. This tends to increase the length and has to drive the master cylinder piston all the way in order to flow. Pressure bleeding in the flow direction can be done without getting the master cylinder piston into the return position. When this happens the column doesn't lengthen.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I agree with the others...your problem is hydraulics. Mine did the same thing after removing and reinstalling the engine, before it was properly bled.

If air in lines is your problem you need to try to figure out how it is getting in (low reservoir?, bad supply hose?). If you correct that then all you need to do is bleed.

I tried several bleed methods unsuccessfully. The way I finally got it bled was below. You need to make sure that the slave bleed nipple is not able to suck in air with the below method (I sealed with teflon tape). You also need a hand vacuum pump.
1. Empty reservoir below master cylinder inlet.
2. Open the bleed on slave, attach tubing to the slave nipple, run into a jar of fluid.
3. Unhook the hydraulic discharge line at the master cylinder (fluid will run out of master cylinder and supply hose).
4. Hook up hand vacuum pump to disconnected tubing and pull fluid through the pipe with hand vacuum pump.
5. Close the slave bleed valve and disconnect pump.
6. Fill reservoir with fluid and allow the fluid to run through the master cylinder (messy).
7. Reconnect the tubing to the mastercylinder.
8. Hook up vacuum pump to slave, open bleed, and pull fluid and remaining air through slave cylinder.

The Haynes manual gives a pressure bleed method using the front right brake to flow fluid up through slave and master cylinder, but my front right brake bleeder was plugged (a problem I will have to correct later). If you don't have too much air in the system you may be able to bleed by doing only step 8, but it sounds like you have a lot of air in there, if the clutch stays down.

Good luck.

__________________
1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold

I had this problem in my 220D and 240D. The problem is the clutch master cylinder. The fluid leaks past the cylinder seals and there is not enough force to release the clutch and then push the pedal back up. No fluid is lost because the construction of the master cylinder reclaims the fluid that gets past the seals. The only fix is to replace or rebuild the master cylinder. You can bleed the system all you want but this will not correct the problem. A rebuild kit is available from dealer and maybe else where. You will need a very small hone for the bore of the cylinder.

Refilling the system by using the brake system as explained in the Haynes Manual works great. All you need is a length of plastic tubing.

P E H

Hi Everyone,

thanks for all the input, i will try all your suggestions and report back to you guys.


regards

This is exactly what my '78 240D does, the guy I bought it from says it needed a new slave cylinder, but my fluid level is fine, can the slave fail but not leak fluid, or is the master cylinder at fault here?