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 02-11-2018, 11:42 AM
Registered User
 
Join Date: Jun 2017
Posts: 26
85 300sd intermittent low brake pedal

I'm going crazy trying to figure out the brake problem on 85 300sd. I started when pretty much all my calipers started leaking, so I replaced all 4 calipers and hoses. After that I realized the pedal would sink so I assumed I over stroked the master cylinder and got a new ATE one. I bench bled the master, then bled from the fittings on the vehicle, then power bleed a gallon of super dot 4 through all the calipers. Now the pedal will intermittently go very low, in my garage it feels pretty good and firm but if i drive it around sometimes it will go almost down to the floor. I am stumped what to do next since I don't see any hard lines that are leaking and I also replaced the booster a few months ago.
Reply With Quote
  #2  
Old 02-14-2018, 12:50 PM
Father Of Giants's Avatar
Registered User
 
Join Date: Feb 2017
Location: Newport News, Virginia
Posts: 973
Wrong section, but did you make sure there are NO air bubbles as the system was bleeding? You need to see a solid stream of fluid thru the tube before closing the bleeder screw.

I suspect you may be losing fluid in your reservoir, thus air may be getting in somehow. Re bleed the brakes and see if you can burp the system of any air bubbles. Also, try to clean the calipers and brake hoses if they are dirty with brake cleaner and then stomp on the brake pedal, check to see if you have any fluid leaking from the hoses or from the seals of the caliper. I was losing fluid and did the "stomp and see" procedure mentioned and found out my rear right caliper was leaking. I didn't bother with a remanufactured caliper and just bought a seal kit for dirt cheap to fix the issue.

If you're not losing fluid from the brakes or lines, then check to see if the fluid reservoir is sealed properly. If you stilk cant find a leak, then you'll have to see if the fluid has gotten into the brake booster. According to the FSM, if a small amount leaks into the booster you're fine. But over a certain amount and the manual demands that the brake booster gets R&R'd.
__________________
1986 Mercedes 300SDL Black - 320,000 miles. Out of retirement

1997 E300 Cream Beige - 218,000 miles new

2000 Mercedes E320 Black - 136,000 miles - New daily driver.

Don't forget to grease the screw and threads on the spring compressor.
Reply With Quote
  #3  
Old 02-14-2018, 01:58 PM
tyl604's Avatar
Registered User
 
Join Date: Feb 2008
Location: Atlanta, GA
Posts: 2,927
You say you bench bled the MC. But as I remember it has two compartments for fluid and the one in the rear is hard to get filled.

Might check that.

I also seem to remember that there is a rubber button/switch on top of the MC and you are supposed to push it to reset. Not sure what it resets. Maybe it is for your low brake fluid light. Of course that would have nothing to do with the pedal going to the floor.

Good luck.
Reply With Quote
  #4  
Old 02-17-2018, 09:13 PM
Registered User
 
Join Date: Dec 2005
Location: Carson City, NV
Posts: 3,768
Check your wheel bearings. I had a similar problem and found that one of my rear wheel bearings had loosened after it was replaced.
__________________
Anyone who thinks a 300D is fast drives too slow.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 357,xxx miles
08 Triumph Street Triple 24,xxx miles, lowered 10mm in front, Pirelli Angel GT tires, EBC HH brake pads, otherwise stock.
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 08:03 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, 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