180E Clutch: Low Pedal Engagement

[cowiepeters]

I have recently purchased a 1993 180E with 188,000km.

The clutch engages only about 1" off the floor. I have read various posts that suggests that this is due to air in the system.

I had to remove the slave cylinder to unblock the bleed screw... a rotten job!

I have bled the system from above twice and "reverse bled" it from the front disc caliper with no success.

Can anyone suggest a solution?

Thanking you!

Peter

[ctaylor738]

More info, please -

What does it do the rest of the travel before it engages? Is it loose, or are you getting resistance immediately from the top?

Can you have someone depress the clutch while you watch the resevoir? Is fluid rising as the clutch is depressed?

Does the clutch slip at all?

[Greg in Oz]

Peter,

Is it engaging so low as to cause baulky gear engagement? I don't mind a low engagement point so long as gear selection does not become difficult. At least there is no risk of clutch slip. As you correctly state, air in the hydraulics can cause the low engagement point. Another cause can be a faulty slave cylinder although since you have already removed yours, you would have noticed if it was leaking. Worn piston seals in the master cylinder could also be the cause without showing up as an external leak. Maybe if we swap parts we might both get our clutches to engage at the correct point! Mine has had the reverse problem to yours of engaging very high in the pedal travel when hot. I will revive my thread on that topic when I get back to sorting it out. Let me know if you fix the problem with yours.

Greg

[cowiepeters]

Greg,

I am sure we know each other from the MB club when I had a white 6.3 and you had the 350SLC, I have followed your posts about the oposite problem with interest

The low engagement point does make smooth changes awkward so I would say it is baulky but there is no problem engaging any gear at rest

I did not observe any obvious external leak when I removed the slave cylinder

Peter

[cowiepeters]

Dear Chuck,

Thanks for the quick reply!

Their is a little "slack" in the top 1/4" of travel then the pedal feels "normal" to the floor ie good resistance.

Their is no evidence of slip except for yesterday after about 1/2 hour of my 16 year old daughter's attempts to learn to drive (the reason for getting the 5 speed in the first place!) It felt a little soggy on the take up as I drove the car home from a quiet area.

I haven't seen if the level of fluid rises as the pedal is depressed.

Peter

[Duke2.6]

Try pumping the clutch rapidly. Does it engage further up? Is there any evidence of leakage at the master or slave?

It sounds like you have bled it, but if multiple bleedings don't work and there appears to be no entrained air, it's probably one of the cylinders. The slave is usually the first to go, so if you replace or rebuild it and the problem persistes, rebuild or replace the master.

Bienniel fluid flushes, along with the brakes, will prolong the life of the hydraulic components, but, unlike the brake cup rubbers which move very little, the clutch system cup rubbers see full stroke every time you declutch and wear. That's why you get all the black crud when you flush the fluid.

Duke

[ctaylor738]

On the assumption that you have all the air out and that the system is tight -

I think that the first thing to do is to find out if you have an adjustment for slack. If you have an eccentric bolt where the master attatches to the pedal, you may be able to adjust it and remove some of the slack. A quarter-inch is a lot. An adjustment would have the effect of moving the engagement higher in the travel.

If you have the non-adjustable version like Greg's, you may be stuck with the fact that you need to move a given volume of fluid to release the clutch. If the disk is worn and the springs in the pressure plate are taking up the slack, then more fluid hence longer pedal travel will be needed to release the clutch.

[cowiepeters]

Thanks for the input so far.

There is no adjustment at the pedal so it appears as if I am looking at three possibilities:

1 Master cylinder worn at top of stroke therefore pushing less fluid than is needed to disengage the clutch...easy to replace, not too expensive, probably due at some stage soon anyway

2 Slave cylinder ditto...awkward job (That top bolt is virtually impossible to get a spanner on... lucky I have long fingers and the surgery to implant double joints in my wrists, elbows and shoulders was succesful. I am looking for a prosthetic hand in a two year old size.), relatively inexpensive, if it was leaking wouldn't the clutch gradually engage itself if the pedal was held down?

3 Clutch plate etc. components worn... BIG JOB!, expensive, it seems to work fine except for the low engagement problem


How does my reasoning & diagnosis sound?

Unless someone suggests otherwise I will tackle it in that order and let you know how it goes.

Thanks,

Peter

87 560SEL, 02 ML500, 93 180E

[ctaylor738]

1 Master cylinder worn at top of stroke therefore pushing less fluid than is needed to disengage the clutch...easy to replace, not too expensive, probably due at some stage soon anyway

BUT IT'S A CLOSED SYSTEM WHEN YOU PUSH ON THE PEDAL. THE FLUID HAS TO GO SOMEWHERE - EITHER TO THE SLAVE TO MOVE THE CLUTCH, INTO THE RESEVOIR, OR PAST THE SEAL AS A LEAK.

2 Slave cylinder ditto...awkward job (That top bolt is virtually impossible to get a spanner on... lucky I have long fingers and the surgery to implant double joints in my wrists, elbows and shoulders was succesful. I am looking for a prosthetic hand in a two year old size.), relatively inexpensive, if it was leaking wouldn't the clutch gradually engage itself if the pedal was held down?

YES. BUT IF IT'S LEAKING, YOU WOULD SEE IT.

[Greg in Oz]

Chuck,

I would expect that Peter's 180E has exactly the same arrangement as my 190E (ie. no adjustment). The 180E is a unique to Australia (I believe) rebadged 190E-1.8 (W201). My brother also owns one (a '92 manual) that I owned for a short time almost six years ago. It would appear that the very first W201s may have had a master cylinder pushrod adjustment but the majority (since the mid '80s) do not. I would expect that Peter's car being a late model ('93) would not have the adjustment since my '90 model does not.


Peter,

Yes, I am who you suspect and I remember you (and your 6.3) well. I have replied to the PM you sent me. I still own the 350SLC (have done for amost 21 years). Re your clutch, are you sure it has a problem? I would consider an engagement point of about 1" off the floor to be fairly normal. As Chuck suggests, 1/4" of slack at the top of the stroke seems a bit much though and almost suggest air still in the system. When you bled it, were you successful in doing so in both the normal and reverse directions? My understanding is that the reverse direction is the only sure way to remove air that rises to the top of the master cylinder.

Interestingly, for those who have followed the (long) story of my 190E clutch, there has only since last night been a change in its characteristics. It is now engaging lower in the pedal travel and, like Peter's clutch, also seems to have a small amount of "slack" or "softness" at the top of the pedal travel. At first I thought I was imagining a change, but again this morning it felt the same. I have only driven fairly short distances since noticing this and it will be interesting if the previous problem of the engagement point moving higher with increasing temperature still persists. I won't post anything on my previous thread(s) until I have something of more substance to report. Apart from the softness at the top of the travel it is now feeling quite normal, especially with regard to the engagement point. It is always a bit worrying when strange faults suddenly "fix" themselves. I am sure there is some issue probably with the master cylinder (as I have been suspecting for a while). Peter, I suspect that if there is a fault with yours it may well be closely related to the fault with mine. We had better keep each other posted and compare notes as we find anything new.

Greg