123 300D Clutch acting strangely
 

With the chill in the air up hear in Cleveland, I guess it is time once again to witness strange "going-ons" with my MB. I have done a search but have not found an answer.

My symptom is that on cold mornings my clutch pedal wants to stay on the floor and grab *immediately* when I lift my foot a fraction of an inch. It won't wait till I get to the normal engaging position which is about 3/8 of the way from the floor. I replaced clutch, plate, and throw out bearing 6 months ago. The pedal always returns when I take my foot off the clutch. After warmup and during the rest of the day, the clutch behaves fine.

I re-bled the clutch from the slave cylinder up so I don't have any bubbles. The brake reservoir has not lost any fluid and remains full every time I check it. I don't see any brake fluid leaks on the underside of tranny or near the clutch pedal. Clutch master and slave and brake master are all still original and never replaced. They look OK on the outside. :)

It sounds like either the master or the slave is not travelling all the way when the clutch pedal is pressed and it is cold outside.

Any suggestions as to if the problem lies in the clutch master or slave?

On a separate note....has anyone ever heard of a MB oil pan rusting through and leaking? I appear to have this problem and looks like I will need a new pan. Pan seal is tight and so is main crankshaft seal.

Thanks,

My first thought would be the clutch slave cylinder needs replacing. Since they are both original I would just replace them both but you may want to start with the cheapest of the two.
I wish I have a manual tranny in my 300D :)

I think the clutch master cylinder is bad. There is no way of telling from the outside. Kits are available to rebuild them but you need a cylinder hone to do it properly. The hardest part is getting the master cylinder in and out from under the dash. To do the initial bleed connect a hose from a front wheel caliper bleed screw to the slave cylinder bleed screw and pump fluid into the clutch hydraulic system by pumping the brake pedal. Make sure the reservoir is full when you start. ~~~~~~~~P E H~~~~~~~~

P.E. is giving you the best method for bleeding the clutch hydraulics, it's the only way to get ALL the air out, but my experience has been if you just bleed it a little with the two person method, then let it sit overnight the bubbles will come up well enough to work fine.

One adder to what P.E. said about hassling with removing and replacing the master cylinder(and he's right, it IS a hassle). There is an eccentric on one of the mount bolts. This should be turned such that you leave a little free play. This will prevent the throw out bearing from riding on the pressure plate fingers constantly. It is only packed in grease and not designed to turn all the time.

Good luck,