W123 Manual Transmission Shifting Problem

[ChadZ]

I've tried to find a thread for this problem, but after days and hours of searching and reading a lot of the collective wisdom in this forum, I have come up empty.

I just replaced the brake master cylinder, clutch master cylinder, and clutch slave cylinder. I bench bled the BMC and did the oil can method to bleed the CMC and CSC. I went to try to test shifting the gears and nothing would engage. So I went underneath and moved the three shift linkages to a neutral position. I went back in the car and I could shift. This is all with the car not running.

I thought all was well, but then I realized I could shift without pushing in the clutch pedal. The pedal felt OK going down and it came back OK, so I'm wondering what is happening?

Did I do something wrong with the shift linkages? Is there still air in the hydraulic line? What would make the CSC stay engaged like that? Do I need to adjust something on the CMC?

Thanks in advance.

[Frank Reiner]

Originally Posted by ChadZ

So I went underneath and moved the three shift linkages to a neutral position. I went back in the car and I could shift. This is all with the car not running.
I thought all was well, but then I realized I could shift without pushing in the clutch pedal. The pedal felt OK going down and it came back OK, so I'm wondering what is happening?
Did I do something wrong with the shift linkages? Is there still air in the hydraulic line? What would make the CSC stay engaged like that? Do I need to adjust something on the CMC?

That the transmission could be placed in any/all of the gears when the engine is not running is not a surprise; there is nothing turning.
If gears cannot be selected when the engine is running an investigation will be in order.

[ChadZ]

Thanks for the reassurance. I have it all up on stands doing brakes and rotors and I didn't want to mess with running it yet. I'll give it a go once it's back down. Cheers!

[Sugar Bear]

Did the problem exist before replacing the 3 cylinders? If not and that is all that was done then it is probably air in the system.

IIRC, there was an early and a late clutch slave or master. Does anyone else remember this? Do you have the old parts to compare to the new for piston depth?

Good luck!!!

[ChadZ]

It shifted fine before. I had a wet driver's carpet this winter and soon realized it was brake fluid, thus replacing the whole lot of hydraulic cylinders. I got FTE replacements and they appeared to be the same as what I took off when I held them side by side.

I recently acquired this '81 240d from my father-in-law who bought it new and I'm just now learning some of the MB nuances. It's been awhile since I've had a manual and I can't recall being able to shift without pushing in the clutch pedal when the vehicle isn't running, so this caught me by surprise when I could do it today.

[t walgamuth]

That is normal operation I believe.

[Sugar Bear]

Try driving it, I don't see a problem at this point. While your working on it, replacing all of the shift linkage bushings, cleaning the shifter mechanism and adjusting the shift linkage makes a huge difference.

Manual 240D...nice car, good luck!!!

[ChadZ]

Originally Posted by Sugar Bear

Try driving it, I don't see a problem at this point. While your working on it, replacing all of the shift linkage bushings, cleaning the shifter mechanism and adjusting the shift linkage makes a huge difference.

Manual 240D...nice car, good luck!!!

Thanks for your support. I did replace the bushings, although they weren’t there anymore, so I know that will make a big difference!

I’m definitely learning a lot and the car is really looking good. These old diesels are pretty interesting to work on.

[Duke2.6]

The clutch system can be tough to fill from the top. When I replaced the clutch slave cylinder on my W201 a few years ago I filled it by opening up the slave bleeder valve a half turn and connected a length of clear vinyl tubing to the brake caliper, which was full of fresh fluid following a complete flush.

Then my helper pushed on the brake pedal and I opened the caliper valve to pump fluid into the clutch slave. The clutch system shares the same fluid reservoir as the brake system, so once there were no bubbles in the reservoir, I was done and the clutch release/engagement was right on. A spray bottle with water washed off the fluid that seeped past the bleeder valve threads, and I topped off the reservoir.

I don't think it took more than about six pumps of the brake pedal to fill the clutch system. Filling it from the bottom up rapidly purges the air.

Duke