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  #1  
Old 01-29-2003, 10:35 PM
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Unhappy Disappearing brake fluid

A while back I posted on the Diesel forum about this, but I figured I might post it here too. A while back my brakes were very soft. I checked the brake fluid and found that the res. for the back brakes was extremely low. I added some fluid, she was good to go. About a week later it was damn near empty again. I pulled all 4 wheels off, and everything was dry. I added more brake fluid and now again about a week or so later, it's down again. Unfortunately with it being an average 20 degs or colder lately, I haven't had the chance to bleed the brakes and check for leaks from the hardlines under the car. It's not leaking from the reservoir either. Is it possible for it to be getting sucked into the brake booster? The level for the front brakes remains at full. Any help would greatly be appreciated, as my car is due for it's state insp. come Feb. and here is NJ they check brake performance.
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1999 MB SL500 (101,000 mi)
1983 Porsche 911SC (149,000 mi)
2004 Volvo V70 2.5T (205,000 mi)
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  #2  
Old 01-29-2003, 10:45 PM
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check from the calipers to the master cylinder, maybe the master cylinder is bad, and leaking
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No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
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  #3  
Old 01-29-2003, 11:08 PM
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Yes it is possible that it's going into the booster, a bad master cyl. can do this. Pull the vacuum line and examine it, it should be dry (no brake fluid). Since yours is a diesel, it may have a little residue from vacuum pump, I'm not sure about that, but I've never seen a diesel with out residue of some sort on everything under the hood. Be your own judge, try smelling the fluid/booster as brake fluid is rather distinctive. Good luck.
MV
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  #4  
Old 01-29-2003, 11:43 PM
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When you take the booster line off, you can make a dip stick out of a piece of plastic tubing and stick it in there. When it bottoms out, blow in the tubing and listen for fluid/air bubbling. That will tell you if any is in there .. then you use same tube to suck it out [ w/vac pump ]
I have seen them fill right up to the vac pipe hole...
The remedy is repacement of rear seal in Master ...

Careful not to puncture the diaphram....
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  #5  
Old 01-30-2003, 01:53 AM
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Question

sorry I may sound stupid...

but are there two brake fluid reservoirs? One for the back and one for the front brakes? I have one reservoir right in front of the booster...
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  #6  
Old 01-30-2003, 02:12 AM
PaulC
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Quote:
Originally posted by Holson Adi
sorry I may sound stupid...

but are there two brake fluid reservoirs? One for the back and one for the front brakes? I have one reservoir right in front of the booster...
...that is probably divided into two compartments.
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  #7  
Old 01-30-2003, 05:26 AM
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Thanks for the quick replies. I will definetly look into the brake booster line.
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1999 MB SL500 (101,000 mi)
1983 Porsche 911SC (149,000 mi)
2004 Volvo V70 2.5T (205,000 mi)
2014 Tesla Model S 85 (75,000 mi)
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  #8  
Old 01-30-2003, 09:05 AM
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Rick,
I hope you're not driving this vehicle until the problem is fixed ...
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  #9  
Old 01-30-2003, 03:01 PM
dweller
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It's fairly common to have a leak at the joint between the master cylinder and the booster. It will show up as a leak down the face of the booster. You might check that too.
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  #10  
Old 01-30-2003, 04:17 PM
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Check by your feet, it may be leaking into the cabin.
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  #11  
Old 01-31-2003, 06:30 PM
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Well I checked the booster and it's in there. I didn't have a hose small enough to fit through the hole, so I used a piece of srap wire. Fed it in and pulled it out and it was covered with brake fluid. Actually you couldn't see the fluid because it was new, and clear. It was all over my hands. SO, I am I looking at a new master cylinder or is there a seal I can replace. It's not leaking down the front of the booster, that's the first thing I checked. I haven't checked inside the car to see if it's gone that far.
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1999 MB SL500 (101,000 mi)
1983 Porsche 911SC (149,000 mi)
2004 Volvo V70 2.5T (205,000 mi)
2014 Tesla Model S 85 (75,000 mi)
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MBCA member
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  #12  
Old 01-31-2003, 08:32 PM
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If you are into fixing, you can get a Master kit..
If the rear seal is gone , so are the other seals.
The kits are cool if the bore on the master is in good shape..
However, an easy repair is a master replacement.

Whichever way , make sure to replace the seal between the master and the booster or you will have a Vac leak....
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  #13  
Old 01-31-2003, 09:13 PM
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I looked at Fastlane and they show 2 master cyl. available. The picture of the one from Teves doesn't show any hardware/seals. The one from Girling (Lucas) shows new mounting nuts and a seal for the mating surface of the master cyl. The online catalog does not list the large o-ring seperately. I guess I would have to get in touch with Phil on this one.
__________________
1999 MB SL500 (101,000 mi)
1983 Porsche 911SC (149,000 mi)
2004 Volvo V70 2.5T (205,000 mi)
2014 Tesla Model S 85 (75,000 mi)
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MBCA member
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