OK, first, Which MC did you replace?
2, what have you done to find the leak in air?
if reverse bleeding the clutch system clears it up, you have either a bad clutch MC or an air leak somewhere in the clutch circuit. hook up the pressure bleed system pump it up to about 10psi, and start looking for fluid to leak out. replace what leaks.
it may take the better part of a day with pressure on the bleeder to cause fluid to leak out, but it should eventually show fluid wherever the leak is.
secondly, it may not be air causing the problem. if you have a bad clutch MC it may just be the seals letting pressure slip by the piston.
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Well, I guess I'm going to try to reverse bleed it again, but I will watch the reservoir for bubbles this time. Hopefully that will rule out the air in the system theory, so I can move on to more difficult ones. Another thought though-- I found that pumping the clutch seems to make it worse, so is this indicative of a faulty mc or possible air in the lines? Anyone know? Also, if I am in fact bleeding it improperly, any advice on better techniques? I basically just have to try to bleed it without letting any air enter, right? I have been trying to do that, but it can be difficult. I'm getting so frustrated with this car.

__________________
1967 W110 200D
1977 W123 240D (RIP)

Be sure that the feed line to the master cylinder is not leaking, and check the pressure line between the master and slave for leaks too. Good luck!

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

i could have missed it but you did say you replaced the CLUTCH master cylinder?

having clutch and then it kind of bleeding away really sounds like a bad clutch master cylinder.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yeah, replaced the clutch master cylinder--- which kind of scares me because I don't really know if I have the receipt or how the warranty goes... I just don't see any leakage from the master cylinder like i did with the first one, so I'm hoping i am just not too bright on the whole bleed thing, but then again i have done it enough times that you would think i would have gotten it right by now.

__________________
1967 W110 200D
1977 W123 240D (RIP)

So how are you doing the bleeding? This is a very simple system, with new master and slave plus no leaks and it still does not work, we better look at your bleeding procedure.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

This is actually not that uncommon. The cause of the original failure is the hydraulic fluid gets old and absorbs water, then the steel lines and master/slave cylinder steel parts corrode and the rubber seals on the pistons get shredded by the debris. This is a dead end loop, in a hard to get to location, making it harder to flush and to bleed.

If you replace one of these items at a time, you will replace them both again shortly thereafter, unless you are lucky. The corrosion of the master and slave, as well as the steel lines is often ignored, so there is no concerted effort to flush all this crap out before putting a new slave or master cylinder in the system. Merely refilling puts the particulate crap back in the working fluid volume and it isn't long before the problem reappears.

In general, it is advisable to replace both of the cylinders in the same repair job, and flush out the lines to get rid of decomposing rubber particles from the hose connection, and rust in the steel tubing. I would not necessarily go so far as replacing the tubing unless you have indications it is not flushing clean.

Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

one comment.

a master clutch or brake cylinder can leak internally and be failed and never leak anything.

in fact that is more common, i think, than leaking out.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

the clutch master cylinder rod has an cam at the junction of the clutch pedal connection, this cam must be set to allow fluid to flow freely from reservoir to slave cylinder, that way your system will always allow any air to flow back to the reservoir while clutch is now used. check this and i haven't read MB instruction but i make sure there is a little bit of play in the rod when not compressed.
its pretty much as the brake master cylinder, as soon ad u apply the pedal that hole is closed by the rubber cup and can compress the fluid.
Larry Perkins

without seeing the car, i would suspect your "new" clutch master cylinder i have been caught out so many times with new parts letting me down. if your brakes are OK, and the clutch is fine after bleeding, it can only be air getting in from somewhere, either from the slave, (has that been replaced?) or from the unions of the pipe, ....replace the pipe (it is so cheap and easy) then either get the new master replaced or the slave...honestly there is nothing complicated or nasty in there

__________________
-------------------------------------------------------
88 709d moved on
82 406 moved on
82 240d moved on
81 230e deceased
79 240d deceased
73 230.4 moved on
96 210 300 td moved on
92 201 moved on
82 280e daily driver
79 300d keeper
81 240d deceased
87 hymer 660s (408) keeper
......................... You can NEVER have too many cars

Sorry if it seems I have abandoned the post here. I thank you all so much for your ideas/insight on the matter. I re-bled my car this time by removing the line beneath the clutch master cylinder and pumping the clutch with my finger over the hole until fluid came out, then I reverse bled.
The clutch has been very strong but it is too early to say if it will stay.
In fact I doubt it will, so I am just waiting.
Anyway, I remember when I installed the master cylinder I was, well, confused--for lack of a better word--on how the rod going into the master cylinder had to pushed into the master cylinder in order to fit the master cylinder in place.
After reading the post of Mr. Perkins here, I think that might be the root of my problem.
However, I originally tried to figure out a way to give the rod some play, so that it is not constantly compressing on the master cylinder but failed in my efforts.
Please, could someone give me a tutorial on setting the cam?
I appreciate so much the help I am getting here!!

__________________
1967 W110 200D
1977 W123 240D (RIP)

if i remember correctly the cam is on the shaft of a bolt. you simply loosten the lock nut on the outside of it and turn the head of the bolt. watching the shaft for play. when you have it where you want it you simply lock the nut on the shaft.

good luck

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Here I am, with the clutch almost to the floor again, getting ready to reverse bleed.
I know the master cylinder is not getting any fluid from the reservoir, because when I reverse bleed, I can only put in so much fluid before I cant squeeze (I use an oil can) anymore.
When I bought the replacement master cylinder it did not come with a piston and I had to use the piston from the old one, which leads me to the conclusion that I just do not have the right sized piston.
I adjusted the eccentric bolt and it bought me a little more time, but I'm still losing clutch by gaining air bubbles.
I have decided to remove the piston and grind it down so it is shorter, hoping this will help, unless someone has some insight.
I know there are 2 sized pistons available, I've seen master cylinders for sale with 2 sizes included, so does anyone know where/if I can purchase the shorter piston without buying a master cylinder?
I only wish I wouldn't have needed the master cylinder so quickly and I would have bought it from a trusty MB parts dealer instead of Autozone...
Anyway, if someone has any advice it would be helpful.
This is my only quarrel with my car.
Thanks!

__________________
1967 W110 200D
1977 W123 240D (RIP)

If you can't push any fluid through from the bottom to the reservoir, then the eccentric on the clutch pedal rod is mis-adjusted.
Look on the clutch pedal arm where the master cylinder push rod attaches.
You will find an eccentric there that you can adjust by loosening the locknut and turning the eccentric.
This will reposition the rod so that the piston is SLIGHTLY open to the upper portion, thus allowing fluid to flow from the reservoir.

Hope this helps,

Thanks Larry. I actually adjusted the eccentric bolt as much as I can, and still am not able to get any results. Any other ideas? Thanks again for your help.

__________________
1967 W110 200D
1977 W123 240D (RIP)