troubleshooting 240d manual 4 speed clutch - next step? - PeachParts Mercedes-Benz Forum

chetwesley · #1 01-15-2009, 06:39 PM

Hi Everyone,
I have a 1979 240d with a manual 4 speed in it.

A couple months ago, the clutch suddenly stopped working. I found that I was low on fluid (dumped in about 2/3 of one of those small bottles of fluid in before it filled up). I was not able to find any evidence of leaking fluid from the clutch master inside or slave underneath.

I have bled the system, and as far as I can tell, there is no air.

I bled it using a pressure bleeder, pumped up to 15-20psi. The bleeder attaches to the cap of the brake/clutch fluid reservoir, and I hooked a hose from the clutch slave cyl bleeder valve to a bottle beside the car. As I was bleeding it, I watched the fluid coming through and it looked solid with no bubbles. I pumped the clutch pedal while it was bleeding, and the fluid moved faster when I did that, and would retract slightly when I let off the pedal, but then keep bleeding at more of a trickle.

The fluid comes out a sort of golden color. I have actually bled it three times now, and put through about 1.5 quarts of fluid, and it has all been that color when it comes out - slightly darker than it goes in.

I let it bleed out about 1/2 of a quart this time, but stopped it as there was no bubbles visible.

Is there anything wrong with this bleeding procedure, or anything I should be aware of? This is my first time bleeding any clutch system and I am just following the instructions I've found here.

After bleeding, the car will still not go into gear with the clutch. It will go into all the gears with the car off. I am able to start the car in 1st or reverse and move it around like that, but no clutch once it is running.

One strange thing is that the pedal sometimes seems like it is offering barely any resistance, and then occasionally, it will have more. I noticed that after leaving the car run for a while that the pedal was harder to push on the first couple tries. I don't know if that is a coincidence.

Does this information tell you anything that I should look at next. I know people have suggested: first bleed, then slave cyl, then master cyl, then actual mechanical clutch repair/replacement, but does what I have explained tell you anything about what might or might not be operating correctly, to save me some time and $ in replacing parts that don't need to be replaced?

Thanks a ton for any help.

Oracle12345 · #2 01-15-2009, 06:51 PM

could have a small leak or a bad slave clyinder, Also could be using the wrong fluid

chetwesley · #3 01-15-2009, 06:54 PM

Quote:

Originally Posted by Oracle12345

could have a small leak or a bad slave clyinder, Also could be using the wrong fluid

Thanks for your response.

The fluid is dot 4 synthetic. I have no way of knowing what was in there before, but I drove it for a few months with no problems before this suddenly happened. What would wrong fluid do?

If it was the slave cyl gone bad, would I still see the fluid move more quickly when I pushed on the pedal?

If it was a small leak, wouldn't the clutch work after bleeding at least for a short time?

Also, I forgot to mention, but after adding fluid initially, the fluid level never went down, so if there is a leak, it isn't a very big one.

leathermang · #4 01-15-2009, 06:54 PM

I have not had to do this myself....
but I have read here on the forum that bleeding it is tricky and a certain procedure must be followed to be sure of good results..
that info can be found in the archives with a search...

chetwesley · #5 01-15-2009, 06:57 PM

Quote:

Originally Posted by leathermang

I have not had to do this myself....
but I have read here on the forum that bleeding it is tricky and a certain procedure must be followed to be sure of good results..
that info can be found in the archives with a search...

Thanks leathermang.

I have read a lot of different methods and have not been able to get a clear answer on what is the best and why. I do know that I followed the method of one person who said that it worked for them. That is why I am a bit confused right now.

Perhaps I will have to try the other method, the FSM method involving the bleeder on the break caliper - but I have heard mixed results on it.

Does anyone know of a way to tell if bleeding has happened correctly? (other than that the clutch works again

)

rs899 · #6 01-15-2009, 07:02 PM

I am in the middle of fixing hydraulic issues on my 240D as well.

Does the pedal feel as stiff as it did when it was healthy and working well? If not, there is still air stuck in the system somewhere.

I changed the master cylinder on mine last weekend and spent most of the next two days (off and on) trying to bleed it using a pressure bleeder as you did. I could not get much progress that way. The only thing that worked was using the factory workshop procedure of bleeding upwards from the right front brake caliper through the slave cylinder. I still don't have it as solid as it used to be (clutch engages too close to the floor), but it seems to work in first and reverse. I am going to do this again this weekend and get the rest of the air out. I used vinyl tubing of two different diameters joined in the middle (the nipples are different) held on with hose clamps.

Rick

chetwesley · #7 01-15-2009, 07:19 PM

Quote:

Originally Posted by rs899

I am in the middle of fixing hydraulic issues on my 240D as well.

Does the pedal feel as stiff as it did when it was healthy and working well? If not, there is still air stuck in the system somewhere.

I changed the master cylinder on mine last weekend and spent most of the next two days (off and on) trying to bleed it using a pressure bleeder as you did. I could not get much progress that way. The only thing that worked was using the factory workshop procedure of bleeding upwards from the right front brake caliper through the slave cylinder. I still don't have it as solid as it used to be (clutch engages too close to the floor), but it seems to work in first and reverse. I am going to do this again this weekend and get the rest of the air out. I used vinyl tubing of two different diameters joined in the middle (the nipples are different) held on with hose clamps.

Rick

Jeez, no wonder it seems there is very little solid info on how to do this! It seems that there is no very reliable method!

Do you have any idea why the pressure bleeding method doesn't work? Is there high spots somewhere in the system where air can sit and allow fluid to just pass by while pressure is being applied?

Someone suggested that rather than using the brake system to back fill, to use a container elevated several feet above to car to back fill the hydraulic system (like the concept of a water tower). I have also seen the suggestion of using a mightyvac.

Are you able to do the brake backfill system by yourself without any help for the opening and closing of valves while operating the pedals?

Also, this is a dumb question, but when people say right caliper, does that mean the passenger or driver side? I can never remember if the right side when people refer to it is the right side while siting in the car, or while looking at it from the front.

lutzTD · #8 01-15-2009, 07:23 PM

not FSM procedure, but I have had good luck bleeding the clutch by putting a pressure bleeder on the brake res. cracking the bleed screw on the clutch slave, putting a clear tube on the bleed screw down to a catch can, and cycling the clutch pedal with my hand until the fluid in the tube looks clean with no bubbles.

chetwesley · #9 01-15-2009, 07:28 PM

I think I understand the back bleeding concept using the breaks, but is there any particular reason why you have to use the breaks to do it?

Couldn't I just adapt my pressure bleeder to use a smaller hose and feed to the bleeder valve on the slave cylinder, and then pump it up, open the slave bleeder valve and allow it to push fluid (and any air) out the top end into the reservoir?

It is just that the back bleeding with the breaks seems so unnecessarily complicated and with so many places to make mistakes with using two different hydraulic systems. Couldn't you apply the same pressure using anything?

lutzTD · #10 01-15-2009, 07:30 PM

Quote:

Originally Posted by chetwesley

I think I understand the back bleeding concept using the breaks, but is there any particular reason why you have to use the breaks to do it?

Couldn't I just adapt my pressure bleeder to use a smaller hose and feed to the bleeder valve on the slave cylinder, and then pump it up, open the slave bleeder valve and allow it to push fluid out the top end into the reservoir?

It is just that the back bleeding with the breaks seems so unnecessarily complicated and with so many places to make mistakes with using two different hydraulic systems. Couldn't you apply the same pressure using anything?

I dont see why it shouldnt work, but in my case the pressure just bubbled out the threads on the bleeder. I never could get the pressure from the bottom method to work for me.

chetwesley · #11 01-15-2009, 07:32 PM

Quote:

Originally Posted by lutzTD

not FSM procedure, but I have had good luck bleeding the clutch by putting a pressure bleeder on the brake res. cracking the bleed screw on the clutch slave, putting a clear tube on the bleed screw down to a catch can, and cycling the clutch pedal with my hand until the fluid in the tube looks clean with no bubbles.

Hi Lutz, yea, you suggested this in another thread, and it is exactly the way I did it this time, and I still don't have a working clutch.

That is what I am trying to figure out - is it the method of bleeding, or is it that something else in the system is broken, and that is why the clutch isn't working.

lutzTD · #12 01-15-2009, 07:36 PM

Quote:

Originally Posted by chetwesley

Hi Lutz, yea, you suggested this in another thread, and it is exactly the way I did it this time, and I still don't have a working clutch.

That is what I am trying to figure out - is it the method of bleeding, or is it that something else in the system is broken, and that is why the clutch isn't working.

when my clutch master went it leaked fluid ever so slightly from the top around the seal. the symptom was that when I was driving it was fine, but if I stopped at a light sitting in neutral, I would not be able to shift into 1st unless I pumped the clutch a couple times. but I knew the slave was brand new so it was easier for me to eliminate all of the usual suspects.

fruitcakesa · #13 01-15-2009, 07:53 PM

I am following this thread closely since my clutch MC has been leaking since before I bought the car.
I have not had shifting problems yet but my reservoir does drain down to the brake mc hose and the brake warning light goes on.
I have ordered a new mc and other parts as I am about to start the refurb of my cream colored 81 and so will learn from you guys.

leathermang · #14 01-15-2009, 08:12 PM

Sometimes I get the impression that people will trust people they do not know anything about because they are alive and post on the forum BEFORE believing the Factory Shop Manual...
That is not a slap at anyone in particular... I have not even read this whole post carefully.... I have seen this repeatedly on this forum...
Unless there is something found to be wrong with the FSM instructions it seems to me that THEY are the people who know how to do these things because they made the cars... sometimes they make mistakes... so it is always good to check for TSB's which were issued to fix prior instructions or parts...
but lacking evidence of that... consider trying the FSM FIRST.. instead of all the other suggestions... you can wear yourself out with all the different ' ideas' posted on some subjects when the FSM might have let you get on with your life and the next project..
I am using the quick reply so I don't have the smilie faces to put at the end of this observation. " SMILE"

winmutt · #15 01-15-2009, 08:22 PM

cough cough.

whats the bottom of the engine/trans look like? brake fluid? rubber part of the clutch line? that fluid is going somewhere.