Bleeding master cylinder - PeachParts Mercedes-Benz Forum

Honus · #1 12-09-2006, 05:20 PM

I just bought a rebuilt master cylinder for my 1985 300D. I put the master cylinder in my bench vise. I attached tubes from the 3 outlets back into the reservior and started pumping. I got fluid coming out of the rear outlets with no problem. On the front outlet, the fluid just barely seeps out of the cylinder when I pump. Shouldn't I have good pressure coming out of each of the outlets?

t walgamuth · #2 12-09-2006, 06:47 PM

your inlet into it may be clogged or the bottom of the plastic res.

tom w

Honus · #3 12-09-2006, 10:35 PM

Quote:

Originally Posted by t walgamuth

your inlet into it may be clogged or the bottom of the plastic res.

tom w

Those both seem to be clear. I can blow back through the tube hooked to that outlet and air bubbles come up in the reservoir with no problem.

t walgamuth · #4 12-09-2006, 11:05 PM

well that leaves the outlet i suppose.

or an internal flaw that prevents it from pumping the front circuit.

tom w

Honus · #5 12-10-2006, 08:47 AM

Quote:

Originally Posted by t walgamuth

well that leaves the outlet i suppose.

or an internal flaw that prevents it from pumping the front circuit.

tom w

As best I can tell, the outlet is fine. I'm thinking there is something wrong with the master cylinder. I'll post this over at the diesel forum and see if any of them have any comments.

SootyPast · #6 12-10-2006, 09:15 AM

No, I would try to bleed it while putting your finger over that outlet to act as a valve. Let it burp out and then close as you retract. I have had them act very stubborn like this in the past taking a long time to bleed.

Honus · #7 12-10-2006, 12:09 PM

I did a combination of methods - finger over outlet, pumping fluid in through outlet, tapping on master cylinder, tilting master cylinder to various angles - and it started working. I guess I gave up too quick the first time. That air was stubborn, though.

Thank you for the responses.