There's a strange problem with my 1980 240d's clutch system. With its engine running and clutch pedal pushed all the way in, you can't shift out of neutral gear. But with the clutch pedal pushed halfway in, you can change gears. There is a very limited area in the clutch travel where you can change gears easily, making the car difficult to drive. Instead of pushing the clutch pedal all the way in to shift, you have to hit this magic zone in the clutch pedal travel. Also, this magic zone moves around.

I bought the 240d with a leaked-down clutch hydraulic system and replaced the slave & master cylinders with ATE & FTE parts. My clutch bleeding method is to use an oil can on the slave cylinder nipple, leave the clutch master dangling, pump the can until no more bubbles are seen in the reservoir, bolt up the clutch master and close the slave cylinder bleed nipple. I found that pressure on the master cylinder push rod blocks fluid flow, and had to bleed the system without the clutch master mounted. I think the system is fully bled.

I've tried adjusting the master cylinder push rod eccentric bolt to no effect, but haven't done the crazy MB adjustment method where you connect the master cylinder to a bottle of water and compressed air yet. I think it has the correct master cylinder push rod (yellowish plastic tip) but there is a longer black one (supposedly for w126) I could try. The W123 haynes manual says to have 1mm play in the clutch pedal before resistance is felt, but who knows if that is accurate.

What could this clutch problem be? I'm not really familiar enough with clutch systems to know if it's a hydraulic issue, pressure plate issue, or even an internal transmission or linkage problem.

Watching your thread....see the one I posted yesterday about difficulty with first and second in my 1981 240D manual!


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I think you may have fallen into the issue of varying push rod lengths (for the master cylinder). I'm not sure that this has ever been fully resolved, but basically MB made at least two different versions of master / slave clutch cylinders for the 123 240D, and if you mix / match then trouble will ensue. Add in aftermarket parts, and you have a recipe for frustration.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

At first reading, the symptoms suggest that there is excess travel of the release bearing and pressure plate fingers, causing them to drag on the clutch disc. With partial pedal depression the pressure plate lifts enough for the disc to be released, with further depression the fingers contact the disc, holding it against the flywheel.
Excess travel could be caused by the installation of a release bearing that is too long, which would cause the fingers to be partially depressed when the clutch is engaged (not enough to cause slippage), but would travel too far when released.

Can any pedal free play be obtained by adjustment of the eccentric? (1mm is not enough) If so, try adjusting to the maximum to gauge the effect. If free play cannot be obtained, the cause will be pushrod length. OR, the location of the mounting holes in the replacement master cylinder places the MC slightly higher on the pedal bracket.

I purchased a Jaguar some time ago .The chap sold it for the same reason .I did find the problem eventualy .The owner had fitted ,,, now it may have been the slave cylinder seal or the master cylinder seal the wrong way about .They have a lip on them and this was facing the wrong way .So it might be worth striping it out and checking .

I adjusted the eccentric push rod bolt to where I feel the most play in the clutch pedal. It seems like shifting has improved slightly while driving the car, but the problem at full clutch-pedal-in still exists, causing poor drivability. It's difficult to get into gear from neutral while the car is stopped.

It's possible I messed up the new slave cylinder before installing it, as I pulled its pushrod out to compare with the original one. The pushrod isn't installed backwards but it might not be seated correctly, so I'll order an FTE slave cylinder just to rule that out. The new ATE clutch slave cylinder I installed came with the car so who knows where it's been.

Before installing the FTE clutch master cylinder, I installed an Exedy clutch master and re-used the pushrod original to the car. Having the same clutch problem and thinking the pushrod/M.C. combination wasn't correct, I ordered the FTE which includes a supposed W123 and W126 push rod.

If I were you, I'd just restrict the depth that the pedal goes in somehow and be done with it, but that's not the answer you want

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

Did you compare bore diameter between old and new? It sounds like the master is too large and / or slave too small. This would drastically alter the pedal to clutch release ratio. ( Making the release bearing move too far. )

This would also account for the very narrow range between clutch released and clutch dragging at bottom of peddle travel.

The bore diameters appear to be the same between the new and old clutch cylinders, around 18mm & 24mm for master and slave.

It's possible the clutch master cylinder push rod is too long. I can't use the factory clutch bleed method (push fluid from the slave cylinder nipple) without unbolting the clutch master first, which seems strange. Maybe the pushrod is supposed to put little to no pressure on the clutch master when the clutch pedal isn't pressed. I could cut down the longer black 'w126' pushrod to test this theory.

There wasn't a spacer between the clutch slave and bellhousing, if that makes a huge difference, I don't know.

After weeks of waiting for parts and blowing an entire GALLON of brake fluid through the clutch system, I think this is the answer for now. A $500 240d's transmission isn't going to shift like butter anyway.

All w124 mastercylinders are the same .But half way through production the changed the pushrod .You should have checked the one removed .With the wrong push rod fitted the clutch wont work right.

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If the clutch master piston is partially depressed,( from a long pedal to piston rod or adjustment issue. ) the slave won't fully release and could pump up to the point the clutch would over stroke.

If you cycle the clutch, leave the pedal up and open the bleeder, do you get a squirt of fluid or just a dribble. Is squirt, the master rod is too long / pedal free play non existent.

Slave cylinders are self adjusting, as long as the slave piston isn't bottomed out in the bore, the rod is proper length. There is a light spring in the slave that keeps the release bearing in light contact with the clutch cover release fingers.

db:

Your first quote, above, is in conflict with your second. If you are not able to bleed from the bottom up, it is, as 97SL mentions, because the M/C piston is partially pushed down past the inlet port. The piston is down because there is NO pedal free-play. Apparently the eccentric adjustment will not provide any free-play. Why? See the first quote, above.

A dribble of fluid.

The original and FTE master cylinder push rods have an overall length of ~93mm. As a test, I shortened the extra pushrod to ~90mm and installed it, and set the eccentric bolt to 'maximum clutch pedal free play'. It's improved shifting while driving, but while stopped, you still can't change gears from neutral with the clutch pedal fully pushed in. And going into reverse grinds unless you have the clutch pedal in the perfect position.

But why whittle the push rod? Maybe I am just missing something here, I am going to throw some ideas out...

*Air still in clutch lines
*Missing clutch slave shim causing pedal travel problem
*Clutch lines internally rusted from air exposure/rubber clutch hydraulic hose defective like a failed brake hose
*Clutch assembly needs replacing for some reason
*Exedy or FTE clutch master cylinders incorrect for 80 240d

Right parts will solve your problem ..

In this case you don't have enough release bearing travel or more likely at this point, the clutch disc is coming apart. Sometimes the disc friction material comes apart and jams against the flywheel causing it to drag.



Pressing the pedal would help clutch disengagement if this was the case.
As long as the piston isn't bottomed or topped out, adding or removing a shim won't make a change.
A swelled hose could cause this however, I'd expect a slipping clutch while driving until fluid made it's way past the restriction. The metal lines won't rust to the point of clogging.

I'd lean towards this.

It is probably OK, you have the dual problem of not enough clutch disengagement and then clutch drag if you push farther. A miss match in rod or bore size would give on or the other.