Vacuum Leak in brake booster

[stephenc03]

I have an 81 240D manual that has a vacuum leak inside the booster. At first I thought it was comming from the vacuum lines near the booster but I got out my stethiscope and can definatly hear a leak comming from inside the booster. What do I have to do to fix it? Do I replace the entire booster or just the diapgram inside or maybe something else? How difficult is it to do? Thank You.
-Stephen

[rrgrassi]

You have to replace the booster. Disassembly of it is not recommended. IIRC there are spings inside under lots of pressure, and you risk bodily harm if you open the booster.

I have not had to replace one, yet, so I do not know the degree of difficulty.

[pawoSD]

Easy to replace, but expensive part. Couple Hundred Dollars.

Step 1: drain brake fluid from resevoir
Step 2: Detach brake lines from master cylinder
Step 3: Detach Master cylinder from brake booster (two nuts on front of unit)
Step 4: Remove Drivers side kick panel cover
Step 5: Hardest step, remove the pin that connects the top of the brake pedal arm to the piston/arm of the booster, then remove the 4 nuts that secure the booster to the bulkhead of the car (not that easy to reach, they're way up in there, you'll have to lay on the floor of the car in an awkward position and reach up in there with a ratchet and good worklight)
Step 6: Pull off the brake booster (be sure to detach vac line)
Step 7: Install new booster, repeat above steps in reverse
Step 8: Re-bleed brake system with new fluid
Step 9: check brakes!
Step 10: drive

Should take less than 3-4 hours tops is my guess

[stephenc03]

Hey thanks, very imformative...I was looking on line and the boosters go for 200 or three hundred dollars. I think my best bet is to scower the junk yards for a good one.

[Ara T.]

There was a website somewhere that sold rebuilt brake boosters, I can't remember it though. I need a new booster as well. If i recall the price was around a hundred bucks. Better than a new $400 one

[W Black]

I had to replace the booster in the 300CD I used to have. Found one in a junk yard for $45.00. I could test it with my vaccum tester before I bought it.
Worked great till I sold the car.

[Surf-n-Turf]

Whooooaa. Check the o-ring between the master cylinder and the booster. Could save you a couple hundred $$$. These boosters are notorious for rusting around that area. That is a common area of vacuum leakage.

[Samuel M. Ross]

Originally Posted by Surf-n-Turf

Whooooaa. Check the o-ring between the master cylinder and the booster. Could save you a couple hundred $$$. These boosters are notorious for rusting around that area. That is a common area of vacuum leakage.

Since I have a 1980 240D I did an OnLine parts check and found this is most likely called a "pinion seal" and cost less than $10.00.

I seem to remember reading something on this FORUM once before that said there is no vacuum on the other side of this seal but the ol memory is not so good any more... so I hope this is your problem. If you isolated the "hissing" to the booster area, you should also be able to determine iF it is coming from around the base of where the master cylinder mounts !?
Here is what our sponsor shows it to look like:
http://img.eautopartscatalog.com/live/J701095383CFW.JPG
... and here is the details of the part:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1WH11JXAQ1YL0MT4RX&year=1981&make=MB&model=240-D-002&category=All&part=Pinion+Seal
Reards,

[Stevo]

If you have too get up under there and remove the booster, take out the drivers seat, it makes the job allot easier. I also do that when replacing clutch master.

[stephenc03]

Hey thanks for all the help. I am pretty sure it is coming from inside the booster but I will definatly check it again before I replace the entire thing. That is funny that you mentioned taking out the drivers seat becuase I just swaped that seat out a month ago from my 300D.
-Stephen

[Stevo]

Originally Posted by stephenc03

That is funny that you mentioned taking out the drivers seat becuase I just swaped that seat out a month ago from my 300D.
-Stephen

Thats good, you know the drill then... I could never do it with the seat in, but I'm old and don't bend as well as I used too

[stephenc03]

Stevo,
Well i guess im a lot younger than you are becuase i'm 21 with a strong back and it doesn't hurt me too much to lay on my back on the door jam with my head inside the cab and my feet resting on the ground. I don't mean to brag but I'm sure it will catch up with me one of these days. Thanks,
-Stephen

[iNeon]

So what are the odds of this problem being limited to a seal between the MC and booster itself?

My brakes are hard as a rock, and I can hear a distinct hiss when I first start the car and press the brakes. The pedal is mushy then, but then the entire time I drive-- not so much.

Mother has been borrowing it lately, and I'd like to not lose the car because she can't press the brakes as hard as they need to be pressed! It's really a non-issue to me-- I've grown to appreciate the loose steering and hard brakes!

[Stevo]

[QUOTE=iNeon;1349504]I'd like to not lose the car because she can't press the brakes as hard as they need to be pressed!

Geeez, and what about your poor mom?

[iNeon]

[QUOTE=Stevo;1349555]

Originally Posted by iNeon

I'd like to not lose the car because she can't press the brakes as hard as they need to be pressed!

Geeez, and what about your poor mom?

1) It's a w123 she's riding in-- she'll be fine, as she only drives around town and to church.

2) My 'poor' Mother has been sitting on 25G's waiting to buy a new car for 2 years-- But what does she keep driving for free?

Yep-- Her son's MB. It warms my heart to know that she's safe and enjoying her drives--

Best mom's quote: Dad asking why she still hasn't bought herself new car... " I LOVE driving that old thing! They don't make them like that now!"

Truer words have never been spoken.