brake bleeding problems! - 1987 300D - PeachParts Mercedes-Benz Forum

solitas · #1 07-29-2006, 10:01 PM

First posting - please bear with me - i'm freaking here...

A 1987 300D, antilock braking, soft brake pedal, spongy - felt like bubbles. Figured to try to purge (edited out:bleed) the system (seemed the first thing to try - fluid a little low). Looked at all brakes yesterday - no leaks/wetness anywhere.

Today: suctioned-out the old fluid from the reservoir, looked a bit dark, filled it with new DOT4. Pedal felt a little better with the engine running.

Hooked a Mityvac to the left front caliper to start purging the lines, pulled about 10" of vacuum, cracked the valve and withdrew a bit of fluid with several bubbles in it. Did it twice more - more fluid & some bubbles. Maybe pulled out just under 2oz. of fluid total. THEN realized it could be leaking air around the threads.

Got someone to help me to play 'pump & hold the pedal, burp the valve". NOW the pedal goes all the way to the floor, hardly any fluid coming out of the tube (what comes out doesn't look as clear as the new I put in) and have tried it 15-20 times with NO improvement.

When the pedal is pumped and held I can still spin the rotor. Haven't checked the other wheels or moved the vehicle yet - left front is still jacked & wheel-off.

HELP!

PLEASE tell me I didn't screw-up the ABS! And what can I do to fix this? This is my first car w/ABS (other cars are '83 MB 240D and '86 VW Jetta - both power & assist but no ABS) and vacuum or 'pump/burp' bleedings have always worked fine on them.

(desperate) Thanks!

whunter · #2 07-29-2006, 10:17 PM

All the data you need.

ShopForum > Do It Yourself Links & Resources > DIY Links by Parts Category
Brake:
http://www.peachparts.com/shopforum/showthread.php?t=142411

Have a great day.

toknow · #3 08-16-2006, 09:03 PM

I have the same problem happened to me today, what did you do to have fluid out there (rear right wheel). I tried pumping with my foot with a helper for about 1 hour and no solution only air coming out.
please help
thanks

Arthur Dalton · #4 08-16-2006, 09:48 PM

You have emptied the master res.
There are two res ,seperated by a wall,, the fluid has to go over the seperating wall to get to the other res.. you have to fill the res to the top for this to happen.

toknow · #5 08-16-2006, 10:02 PM

Hi,
I filled the reservoir to almost the top.there is no fluid moving out of it to the other res. I assumed both filled. Can you tell from outside the res. if the back one is filled. is the back one so narrow that you confuse it with the body of the res. It is so redicules from MRBZ to design the res. this way. I heard about this 10 times already and stil confused. Sometimes there is something in the design that only the designer can see, it seems stubid to the others. may be I missing something else. I will check again tommorow,
thanks

Arthur Dalton · #6 08-16-2006, 10:27 PM

You have to look at both res.
The only way to fill the back one is to over-flow the front.. this is a dual braking system and requires the 2 res.

If you do not have them both full, you are wating your time .. and only making things worse by pumping air into the entire system..

t walgamuth · #7 08-16-2006, 11:09 PM

the system is designed this way for your safety.

if you blow a seal or line on the rear brakes (or the front) and empty the mc of fluid you can only empty the side that is feeding the failed part of the system. the other side is there for you and you can stop the car.

you dont want it to have no fence. trust me.

tom w

wbain5280 · #8 08-17-2006, 12:22 AM

With ABS, it's best to pump the brakes 50 to 60 times to purge the accumulators, then prodceed with bleeding. Forget the Mighty Vac, get a pressure operated bleeded, such as this one:

http://www.ipdusa.com/ProductsCat.aspx?CategoryID=1595&NodeID=5088&RootID=629

which will also work on MB's. I know, I've used it on Volvos and MBs.

toknow · #9 08-17-2006, 02:44 PM

Problem fixed!
It was again the back reserviour. It was all empty that is why I could not see any oil level, i thought it was all full. I just cannot understand why it is not larger than that and more visible. I read in this forum that many people encountered thjis problem. My car 1s 1987, hopefuly in the new designs MRBZ fixed this.
For anybody with this problem, you need to check the back, the container is then (1/2 inch thick) looks like the back wall of the reserviour. there is a mark (not very visible) says MIN. the oil level could go easily passed this mark down while bleeding before you notice. To fill the back, you need to add the fluid untill the little hole in the neck of the res. also, the level of the car is important. You need to pump the brake pedal gently until the fluid migrates to the back. it needs patience!!!
Thank you all for help.

whunter · #10 08-17-2006, 09:18 PM

Brake bleeder recommendation
http://www.peachparts.com/shopforum/showthread.php?p=455818

Power Bleeder or what?
http://www.peachparts.com/shopforum/showthread.php?p=707359

Brake bleeder - power bleeder Homemade
http://www.peachparts.com/shopforum/showthread.php?t=117258

Industry Adopts Brake Fluid Replacement Guidelines By Bill Williams, Technical Contributor
http://www.babcox.com/editorial/bf/bf50412.htm

Brake flush every two years?! U'r kidding right?
http://www.peachparts.com/shopforum/showthread.php?t=96852&page=1&pp=15

Why should I flush my brake fluid every year, you ask?
http://www.peachparts.com/shopforum/showthread.php?p=220599