Weird Clutch Problem 1998 C200
 

Hi All,

I have a 1998 C200 manual transmission.

I'm having a clutch problem whereby after extended driving on the freeway, the clutch will battle to disengage and the clutch pedal gets very soft. After pumping it a few times its normally fine. Also with the clutch feeling soft, the brake pedal also seems a bit softer.

We went on a long (400km) trip this weekend and it did the same thing. However it eventually wouldn't go back into gear.

I therefore parked the car and fetched my other car to tow it. When we returned to the C200, after about half an hour, we decided to try the clutch again and it worked fine?

What could be causing this? This doesn't happen when my wife drives around town every day. There also doesn't seem to be a drop in the brake fluid level.

If it's relevant we live in Durban, South Africa where the average temperature currently is +-30 deg C (+-86 deg F). I wouldn't think its heat related as to me town driving would be hotter on the clutch lines than high speed freeway driving with plenty of air flowing through.

Please help!

Thanks,
Jase

Anyone?

Has the fluid in the clutch hydraulic system and the brake system been flushed? This should be done every 2 years. The boiling point of brake fluid decreases substantially as it adsorbs water. If it hasn't been flushed I would do so. Be sure to use DOT 4 approved fluid. Mark

Keep in mind, if you don't get too many responses right away, there hasn't been a Mercedes with a clutch in the US for a while... AFAIK

Not sure but the SLK 320's (2004) may have been the last manual trans. MB's over here. Mark

I replaced the line running over the gearbox to the slave cylinder last year. At this stage I flushed the brake/clutch fluid. Perhaps I should do it again... I can't remember if I did all the brake lines as well or just the clutch line. I used a pressure bleeder pushing fluid through the bottle to the slave cylinder bleed nipple... Is that correct?

Thanks,
Jason

As stated by a previous poster there is not much opportunity to see manual transmission MB's in the states so excuse my unfamiliarity with the system on your car. A forum member with experience on your car or access to WIS should chime in.

Generally speaking, your bleeding process should work. Doubtful that lowered boiling point of the brake fluid is the cause. Are you sure about the quality of the brake fluid you used? Sealed container, proper DOT rating as recommended by MB (yours may be DOT 5.1, not 4) from a reputable manufacturer. Peel back the rubber protective boot on the slave and master cylinders to check if brake fluid is leaking. I would also bleed the system again. Is the slave cylinder installed with the bleed nipple pointing upwards. Is there adjustment for freeplay in the clutch pedal (short movement of the clutch pedal before it begins to depress the master cylinder piston) or slave cylinder? Good luck. Mark

repeat the flush trying to get as much air out as possible and as much new fluid through the system as possible. Try bleeding the clutch system manually as well. Once done, if the problem still persists then there is some kind of mechanical problem causing this issue.

Ok guys, I'll redo the flushing and try buy clutch fluid from Mercedes if they have here. That way I know I'm putting in the good stuff.

Not sure when next I'm doing a long trip but I think I'll drive the car for a while to keep an eye on it.

My wife won't mind as she loves driving my 230E Sportline (Auto)...

Will post again once I have a verdict.

Thanks,
Jase

Ok, I checked under the car yesterday whilst greasing the ball joints and it seems the line running to the slave cylinder is leaking on the opposite side of the gearbox to the slave cyclinder. I replaced this line last year but the join that was made up for me where the flexi hose meets the solid line seems to be the fault point...

Strangely I haven't noticed a decline in the fluid level but I'm sure the fluid must be contaminated with moisture by now and therefore the boiling point of the fluid has decreased resulting in my symptoms only after high speed driving and high exhaust temperatures.

So I need to repair that line, again, and I have a question. Is it ok to install one of those flexi lines with the stainless steel braiding around or do I need to use the stock setup of a solid line fused to a flexi line. The solid section is used to run over the gearbox. Will there be any issues changing this to flexi line?

Thanks,
Jase