Clutch Bleed Help - 240D Manual Transmission - PeachParts Mercedes-Benz Forum

Sulawesi · #1 05-30-2010, 04:15 PM

Hi All,

I've followed most of the threads on bleeding the clutch. The most successful episode was running the hose from the right brake caliper, opened both bleeding valves, and using the brake pedal to bleed the system until I observe no bubbles at the master cylinder.

This method worked, but when I went for an immediate test drive, within 5 mins of driving, the pedal softened until shifting was once again difficult, reverse impossible. I repeated the bleed, and obtained the same short lived repair.

To back fill why I figured I have a hydraulic problem only, I was driving and I noticed the brake pedal was soft, and doh, realized the fluid had rum low in the master cylinder reservoir. I topped up the reservoir, brakes were fine, but clutch was soft, so I assumed I had air in the lines. I dutifully read the forum, and tried the brake caliper method, but as described above, my positive results have been transient. Any ideas what I am doing wrong?

JEBalles · #2 05-30-2010, 04:51 PM

Sounds like you've got a leak in your clutch hydraulics. Check around the master and slave cylinders for wet spots.

Sulawesi · #3 05-30-2010, 06:28 PM

Would a leak soften the clutch without emptying the reservoir...I was figuring I must not be getting all the air out. I will check of course, thanks.

#4 05-30-2010, 07:06 PM

I finally learned that on the 123's if you will do a regular two man method bleed and then let it set overnight, enough bubbles will work their way to the top that it will work fine. If there are no leaks anywhere, I expect that this will work for you.

Sulawesi · #5 05-30-2010, 08:18 PM

that is easy enough to try...thanks.

yellowbenz · #6 05-30-2010, 11:00 PM

I've bled the clutch hydraulics on my 240D with the one man technique and it works. However, I've had two experiences, one with a 190D and the other with the 240D, in which the system bled itself after a few days. It probably helped that the 240D was parked on a significant slope. I don't know if this helps but any information about this can't hurt. It seems to be recurring problem to get these systems bled after master/slave replacement. Have you checked the master or slave to see if they are leaking? First inkling I had was when my Brake light came on indicating a leak. Looked under the mat and found a collection of brake fluid leaking down the line from the master. Slave cylinder should leave a spot under the car.

Sulawesi · #7 05-31-2010, 09:40 AM

I've seen the "parked on a slope" comment before. Is this an upward slope or a downward one?

yellowbenz · #8 05-31-2010, 09:51 AM

Nose up. Based on the difficulty with active bleeding, I didn't think it would work but the laws of physics are immutable I guess. Until you find why you lost brake fluid, though, this will likely only be a temporary solution.

Sulawesi · #9 05-31-2010, 10:43 AM

I think it leaks very slowly between the mast cylinder and the reservoir. There are stains of past leaks (car is relatively new to me) and slight moisture.

Sulawesi · #10 06-05-2010, 07:24 PM

Please tell me what I am doing wrong. I want to drive my lovely old Mercedes!

I tried to bleed the clutch the 2 person way. I open the bleed valve, partner depresses the clutch pedal, I close the valve, they release. The problem here is that after two pumps I have lost all the hydraulics and depressing the clutch results in almost no brake fluid being pumped through...there is no chance to purge air.

So, I revert to using the right brake caliper, with a hose extending to the slave, opening both bleed valves, and using the brake to purge air. It works, the clutch pedal returns to normal. I park the car nose up for days.

Today I drive it an within two miles I have no reverse and my clutch pedal is back the way it was. I am getting frustrated.

yellowbenz · #11 06-05-2010, 07:43 PM

Just my .02, but I think this will continue to be a problem until you identify what's wrong with the clutch side of the hydraulics. Master, slave, or both?

charmalu · #12 06-06-2010, 01:54 AM

What is the original reason for bleeding the clutch system? Did you replace the master or slave cylinder? Or did it suddenly start giving you problems?

the reason for bleeding from the bottom up, is air rises.
I used my Motive brake bleeder, and power flush from the top down.

I pwr flushed from bottom at the slave cylinder. Be careful on this one, you don`t want the brake reservor to over flow.

I uses the FSM method several times. Be sure to purge the air out of the line before connecting to the slave, or you are reintroducing air into the system.

Had wife pump peddle and open the slave bleeder.

It was this last method that suddenly my wife said, "it works" it seems firm.

Iam not sure what got it to working, maybe I was holding the wrench differently the moment it worked

.

I had an Indy tell me he power flushes from the bottom up, and to tap the MC with some lite taps to dislodge any air that could be traped in there.

Charlie

Stevo · #13 06-06-2010, 11:20 AM

Quote:

Originally Posted by Sulawesi

Please tell me what I am doing wrong. I want to drive my lovely old Mercedes!

I tried to bleed the clutch the 2 person way. I open the bleed valve, partner depresses the clutch pedal, I close the valve, they release. The problem here is that after two pumps I have lost all the hydraulics and depressing the clutch results in almost no brake fluid being pumped through...there is no chance to purge air.

So, I revert to using the right brake caliper, with a hose extending to the slave, opening both bleed valves, and using the brake to purge air. It works, the clutch pedal returns to normal. I park the car nose up for days.

Today I drive it an within two miles I have no reverse and my clutch pedal is back the way it was. I am getting frustrated.

You dont need two people for this operation. Simply hook up the hose SECURELY between the clutch slave and brake slave and, from outside the car, with your hand, pump like crazy many times, crawl under, close both bleeders and try the clutch pedal. If you dont have the clutch, repeat the pumping, NO opening and closing the bleeders between pumps, just pump.

Sulawesi · #14 06-07-2010, 08:46 AM

The original symptom was a soft brake pedal, once, an empty rear reservoir, and then a soft clutch. MY failure to bleed the system makes me think there is more going on then just letting the fluid lapse, as some posters suggest.

The problem is, I am not sure where to start. The brake master cylinder has leaked at the booster. It seems like that is a good place to start, and this means flushing out all the brakes.

OK, but what if the issue is with the slave or clutch MC? There is no sign of leakage there, but part of me says spend the extra $100+ and replace those, bleed the hell out of the system, and be done with it.

Any advice on the appropriate sequence of events, it seems clear that the brake MC is first in line with the leakage (I also fear for the health of the booster if the leaking persists.

PS: Parts history, Clutch MC was replaced in 1994, 70K miles ago. I have no records on brake MC and clutch slave, so I must assume they are original (180K miles).

Thanks for all your thoughts...

Stevo · #15 06-07-2010, 09:49 AM

Replace the brake master cylinder, bleed the brakes then the clutch and that should solve your problem. your clutch system got air in it because the brake master cylinder leaked down. Check for brake fluid in the booster when you remove the m/s.