Brakes - Help - Mercedes-Benz Forum

 
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 08-04-2011, 05:26 PM Thread Starter
BenzWorld Junior Member
 
Date registered: Sep 2010
Posts: 19
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Brakes - Help

I've changed the brake booster on a '68 280 S, used the correct booster and bled the brakes at the wheels. The master cylinder is full. The pedal is firm and there is no vacuum loss sound (hissing air) or change in idle when I apply the brakes.

The problem is that the car seems to require too much pedal pressure now.

I'm concerned that I might be braking on only two whelels. Is the new (used) booster suspect?

Could this be caused by incorrect bleeding?

Thanks for the help.
copppper is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 08-05-2011, 05:31 AM
BenzWorld Member
 
Date registered: Jul 2009
Vehicle: 1964 Mercedes 220Sb
Location: Muskegon, Michigan
Posts: 103
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
I can tell you how to test a booster...
- with the car off pump it until the vacuum dissipates (usually 2-4 pumps) the pedal should be very firm. (this will tell you if there are any major leaks, a leaky booster will never become firm)
- holding the pedal, start the car, you should feel the pedal drop 3"-4" (This verifies a presence of vacuum in the booster, if the booster is not receiving vacuum pressure the pedal will remain firm and not drop)

After that go from there...
-Incorrect bleeding usually results in a "squishy" or soft brake pedal that has no definite stop to it.
proper bleeding is done with the car off and watching the brake fluid reservoir making sure to not run out of fluid and add air to the system:
(2 person): press brake pedal and hold, have other person open bleeder until bubbles/fluid stops flowing, close bleeder, lift foot off brake pedal and repeat until clean fluid flows out of bleeder with no bubbles in it.
(1 person) attach a hose to the bleeder submerge end of hose in a cup half full of brake fluid, open bleeder, pump brake pedal until clean fluid comes out bubble free, close bleeder.

I've always preferred 2 person as it is less messy and in my opinion easier to decide when the fluid is clean, but they sell one man bleeder kits in all the autoparts stores, they also sell one-way bleeder valves for cars, that make bleeding brakes very easy, but you probably wouldn't find any that fit a 1968 Mercedes.

-other possibilities include collapsed brake hoses on the calipers and rear axle preventing the fluid from moving, but this usually results in rubbing brakes as they are not disengaging.

Last edited by tgikal; 08-05-2011 at 05:45 AM.
tgikal is offline  
post #3 of 4 (permalink) Old 08-05-2011, 07:55 AM
BenzWorld Senior Member
 
Date registered: May 2007
Vehicle: 64' 220SEc, 72' 300SEL 6.3, lots of parts
Location: San Diego/Spring Valley
Posts: 512
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
I had the same issue until the front hoses were replaced,
Internal collapse (swelling closed).

The visible clue was a lack of volume when bleeding front calipers.

Brian O
bostosh is offline  
post #4 of 4 (permalink) Old 08-05-2011, 09:34 AM Thread Starter
BenzWorld Junior Member
 
Date registered: Sep 2010
Posts: 19
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Thanks. Good advice.
copppper is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > Vintage Mercedes-Benz

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Similar Threads
    Topic Author Forum Replies Last Post
    R129 With Silver arrow brakes, upgrade to R230 brakes? spitfire980 R129 SL-Class 18 10-25-2010 06:42 AM
    Buy my stuff , getrag swap/400e brakes/c36 brakes/strute bar veedubfreak86 For Sale/Wanted/Trade/Giveaway 0 08-23-2010 07:29 PM
    Brakes Question (Changing my Brother in-Laws Brakes, Just to be sure) Donkeykongohio W203 C-Class 3 11-27-2009 10:20 AM
    2003 C230 Sedan brakes to 2004 cross-drilled brakes? aaronmarks W203 C-Class 1 10-05-2005 05:00 PM
    Upgrading to Brembo or Porsche brakes? I will buy your W202 AMG brakes from you! Guest (MBNZ) W202 C36 AMG, C43 AMG 1 05-11-2002 03:11 PM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome