Brake Booster replacement. - PeachParts Mercedes-Benz Forum

pj67coll · #1 10-22-2007, 04:37 PM

It's now critical that I replace the brake booster and master cylinder on my 240D. It's leaking so bad I have to fill the resevior once a week and the paint is completely peeling off on the booster and the chassis and firewall underneat it. I have pulled a complete unit from a 300D in a boneyard. I can see no obvious differences between the two just by eyeballing them so my question is would it be a straight swap or is there something I'm not aware of thats different between them. Does the fact that my car is a manual transmission make any difference? I'm a complete noob at this so any thought's would be appreciated.

- Peter.

toomany MBZ · #2 10-22-2007, 05:11 PM

Should be a straight bolt up, the line between the vac pump and booster, may be different.

winmutt · #3 10-22-2007, 05:46 PM

You will need to cut the nipple on the brake fluid reservoir for the clutch line... This junction might be where it is leaking from? In order to do the booster, remove the under dash cover and use some socket extensions, you can feed them right through the wiring and easily access the bolts on the booster. socket extensions horizontal to the ground. Sure beats cramming in there. If you are a big person remove the drivers seat.

pj67coll · #4 10-23-2007, 12:43 PM

[QUOTE=winmutt;1653722]You will need to cut the nipple on the brake fluid reservoir for the clutch line... /QUOTE]

Does the Haynes manual show or describe this nipple? I'm not at home for the next couple of days so I can't look at it. If not can you describe exactly what you mean by it? I didn't see anything obvious when I looked at it last night. I'll be replacing the entire booster along with the mc.

- Peter.

winmutt · #5 10-23-2007, 01:47 PM

[QUOTE=pj67coll;1654492]

Quote:

Originally Posted by winmutt

You will need to cut the nipple on the brake fluid reservoir for the clutch line... /QUOTE]

Does the Haynes manual show or describe this nipple? I'm not at home for the next couple of days so I can't look at it. If not can you describe exactly what you mean by it? I didn't see anything obvious when I looked at it last night. I'll be replacing the entire booster along with the mc.

- Peter.

On the plastic reservoir , rear fender side, there is a nipple and a hose that hooks to it that leads to the cabin for the clutch. Get the FSM from MBUSA and keep the haynes around for bathroom reading or wiping take your pick.

Stevo · #6 10-23-2007, 01:55 PM

I did one in a TD once and it was easy but if your 240D is manual its a little more of a hassle (more stuff in the way), I had too take the seat out.

dbn1066 · #7 10-23-2007, 02:28 PM

I just did the job myself a few weeks ago. Took about an hour to remove the old one and put in the new one from junkyard 300D. I did not swap master cylinders so it was easier. I still had to disconnect the brake lines from the old master to get the old unit out. I was too worried about bending those old lines too far and springing a leak. So I guess this doesn't help much since I didn't have to deal with the clutch issue. But that aside, it took longer to gravity bleed the brake lines than it did to crawl under the dash and unbolt one, bolt on the other.

MBeige · #8 10-24-2007, 12:35 AM

I'm thinking I have to do this soon. Does the brake booster just come out with fasteners I can access from the engine bay or do I have to go under the dash?

I guess together with this I'll also have the rubber brake lines replaced to be on the safe side.

toomany MBZ · #9 10-24-2007, 01:13 AM

On a 123, you'll need to remove four bolts from inside, above brake pedal. Being a contortionist is helpful.

DeliveryValve · #10 10-24-2007, 01:29 AM

Quote:

Originally Posted by dbn1066

I just did the job myself a few weeks ago. Took about an hour to remove the old one and put in the new one from junkyard 300D. I did not swap master cylinders so it was easier. I still had to disconnect the brake lines from the old master to get the old unit out. I was too worried about bending those old lines too far and springing a leak. So I guess this doesn't help much since I didn't have to deal with the clutch issue. But that aside, it took longer to gravity bleed the brake lines than it did to crawl under the dash and unbolt one, bolt on the other.

No you don't need to disconnect them. If the brake lines are in good condition and have no corrosion, then you can gingerly "persuade" the master cylinder to go forward and to the side toward the engine. You will not have any leaks. Then you will have enough room to remove the booster.

MBeige · #11 10-24-2007, 02:43 AM

Quote:

Originally Posted by toomany MBZ

On a 123, you'll need to remove four bolts from inside, above brake pedal. Being a contortionist is helpful.

That's what I feared, I already replaced the brake pedal switch since it was sticking. Yep, had to be a contortionist to get to that thing.

pj67coll · #12 11-19-2007, 05:27 PM

I'm updating this thread finally because I've just managed to do this job today. I know I'll have to bleed the system and I've been reading up on how do do so and frankly I'm at a bit of a loss. The brake pedal hisses and goes easily to the floor, but it does stop the car from a push roll in the parking lot. The clutch however just flops to the floor and I have to pull it back. So I'm sure I'll have to bleed the clutch but how? Is the cylinder on the inside of the firewall that the braided clutch hose goes to the master or slave cylinder and how do I bleed it? Do I unscrew the bolt at the bottom of it and let fluid just run down from the reservoir or what? I'll have to replace the braided hose as well as it's leaking fluid out badly now as well. Didn't notice that before I did this job. This week has gone from bad to worse and I'm almost at the point where I'm about to junk this car. I just don't know if I can take anymore.

- Peter.