trouble shooting brake fluid leak
 

I'm helping a friend with his manual transmission 79 300D. The clutch pedal went soft a few days ago. The fluid reservoir was very low. I refilled it which didn't fix the problem, so at the very least the clutch needs to be bled.

I've looked for leaks around the master and slave cylinder and haven't found anything obvious, however there is brake fluid dripping off of the bottom of the transmission bell housing. The drip accelerates if I pump the brake pedal.

Is there any hose or brake line around the top of the transmission I should be looking for?

The line from the master clutch cylinder to the slave cylinder on the side of the bell housing.

There is a rod in the end of the Slave cylinder that pushes against the throw out bearing lever.
the seal around the rod is leaking, that is why you see fluid leaking from the bottom of the tranmission.

You will need to replace the Slave cylinder.

It has been recommended that is the slave is replaced, the master cylinder will go next, (Vice versa) so do them both now, and save a headache later having to go back in again.

Here is a good video showing how it all works, and bleeding procedure.
He says BMW, but the mercedes is exactly the same.
http://www.youtube.com/watch?v=wdf--suwqw0


Charlie

X2 on the diagnosis and repair. Like Charlie said, the fluid coming out of the bell housing weep hole is from the failing salve cylinder seal.

Cool, thanks for the feedback. Has there been a good write-up done on replacing the slave cylinder? I've done some searching but haven't found anything yet.

Not sure if there is a dedicated step-by-step DIY, but check out post #2 in this link:

http://www.peachparts.com/shopforum/diesel-discussion/299032-tools-replace-clutch-slave-cylinder-1983-240d.html?highlight=slave+cylinder

Charmalu gives most of the details and provides a link on bleeding the system.

Thanks again for the input. Replacing the slave cylinder seems to have resolved the issue.