1969 280S clutch pedal stuck and leaks
 

I was at a stop sign and pushed in the clutch pedal and the pedal stayed pushed down to the floor and would not return. It stayed that way for about a minute (a very long minute!) while I jiggled it with my foot. It finally returned and worked normally so I could get home.

I looked under the dash and found that the master cylinder is leaking at the top where the piston comes out. Would the leak account for the sticking pedal?

I ordered a new cylinder and I’m gonna try to install it myself because of money. Any and all advice and tips gladly accepted!

Leaking master or slave, low fluid or bad adjustments can cause the pedal to stick to the floor.

The replacement cylinder came in the mail. It doesn’t have a rod so I assume I am supposed to re-use the one I have. I wonder if the rod simply pulls out of the cylinder? I can’t really tell with the new one because the rubber boot hides everything.

Also, do I need to drain the system down at the slave cylinder or can I just remove the fluid from the reservoir and not end up with a geyser erupting under my dash before I can plug the lines?

My car does not have a separate clutch reservoir but instead uses the brake reservoir. I think I figured out which of the tandem brake reservoirs feeds the clutch cylinder.

I haven’t had much luck finding any step by step directions for this. I once rebuilt the master brake cylinder on a Triumph Spitfire but that was 30 years ago.
Any help or links or diagrams would be great, thanks!

Well I got it done finally. I had to replace the hose running from the reservoir to the master cylinder and that caused a little head scratching. I had everthing assembled and topped up but the cylinder failed to fill up with fluid. Finally I realized the hose was routed in an arc above the level of the reservoir. I pushed the hose down and air bubbles began popping up in the reservoir. Duh.

Thanks for posting this query. My '67 250S has the same brake/clutch reservoir, and clutch master and slave cylinder layout (both cylinders have bleeder valves).

After replacing the clutch master cylinder did you bleed both the master and the slave cylinders? I'm guessing that the master should be bled first since the slave draws fluid from the master. And if the master is removed and swapped out, the slave will have to be bled because of air introduced in the process. Does that sound right? Thanks

I've considered draining the brake/clutch reservoir, plugging up the clutch line outlet, and adding a dedicated clutch reservoir.

Good question. I really don’t know much about hydraulic systems but I’ll tell you what I did. The only directions for changing the master clutch cylinder that I could find were for a W201 Mercedes and I followed that.

The guy that wrote it said (and I don’t know if he knows what he’s talking about) that “basically the [master] cylinder is the very upper point of the hydraulic system so there’s no need in bleeding.” Remember, I have absolutely NO idea if he knows what he’s talking about!!

My master cylinder doesn’t appear to have a bleeder valve. So I didn’t bleed it or the slave cylinder either. I followed the guy’s directions to refill the reservoir and to pump the clutch pedal several times (pulling and pushing it fully until air bubbles stopped appearing in the reservoir).

The clutch appears to operate fine now but I made a promise to myself to bleed the system properly as soon as I can (just in case that’s the best practice). So far, the instructions I’ve found for doing proper bleeding are confusing to me.