Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 11-09-2004, 07:42 AM
Registered User
 
Join Date: Mar 2004
Location: Kansas City, MO, USA
Posts: 1,213
Bad Master Cylinder?

A few days ago, I noticed that when I first step on the brakes on my '84 300SD (no ABS) they feel firm, but then as I wait further at the traffic light for which I braked, they start to soften and loosen and I'd then have to push the pedal almost to the floor to completely stop the car. Sometimes this would happen, some other times it wouldn't. The situation is getting worse as sometimes even as I approach the light, the brakes would be soft right away and I'd have to push them to the floor to stop the car.

My mechanic and I closely inspected the situation. For some strange reason, the level of the brake fluid in the reservoir had risen!! Just less than two months ago, I had the rear brake pads and rotors replaced. The front ones, while thin, are still usable, so that's not the cause of the problem. My mechanic drained the excess fluid from the reservoir. Upon pumping the brakes with the car turn off, we could hear a noise (sounded like a leak) that comes off the master cylinder when the brakes are pumped. At that point he concluded that I needed a new master cylinder. He explained that the failure of the pistons in the master cylinder to hold pressure was resulting in the fluid not recirculating as it should, thus the increase in the amount of the fluid in the reservoir.

I did several searches here, and while there was no thread that directly addressed my issues, I learned that (1) it can't be the brake booster as the pedal would be really hard if that were the case (2) considering that my car had just 145K when I purchased it, 20 years after its manufacture, such premature wear of the master cylinder isn't unusual as the car was mostly driven in the city all its life. Are all these correct?

I intend to keep this car as long as God allows me to. So I should just buy a brand new, not rebuilt one, right?

__________________
1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver
Reply With Quote
  #2  
Old 11-09-2004, 11:48 AM
Registered User
 
Join Date: Sep 2004
Posts: 8,971
If the original master cylinder lasted 20 years and 156K miles, its demise would hardly qualify as "premature." My vote would be for a new one.
Reply With Quote
  #3  
Old 11-09-2004, 11:56 AM
yal's Avatar
yal yal is offline
Benz-smart
 
Join Date: Oct 1999
Location: New York, Long Island
Posts: 2,707
I vote new one too. Pronto!
Reply With Quote
  #4  
Old 11-09-2004, 11:58 AM
nglitz's Avatar
Registered User
 
Join Date: Aug 2004
Location: Hamilton Square NJ, near Trenton
Posts: 391
There's a seal in between the front and rear pistons in the master cylinder that's leaking. It lets brake fluid go from one part of the reservoir to the other. The seal probably costs 10 cents and $100 in labor to remove, completely disassemble the MC and replace it. Or, a nice rebuilt cylinder for half that.

Enjoy,
__________________
Norm in NJ
Next oil change at 230,000miles
Reply With Quote
  #5  
Old 11-09-2004, 12:27 PM
Registered User
 
Join Date: Mar 2004
Location: Kansas City, MO, USA
Posts: 1,213
Thank you all for your responses. Now it's time to check the prices... calling Phil...


Quote:
Originally Posted by tangofox007
If the original master cylinder lasted 20 years and 156K miles, its demise would hardly qualify as "premature." My vote would be for a new one.
Well, I can understand you well, but my mechanic said that 156K is too soon for a master cylinder to fail, especially one from Mercedes-Benz. He attributed it to the fact that it was really old though.

__________________
1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 08:43 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page