Something is up with the brakes on the car. The back reservoir (the one closest to the firewall) was low on fluid. So I topped it off and bled the brakes all the way around. (Btw no leaks in any of the rotors) Well after that the brakes were still very very weak. I looked at the master cylinder reservoir and the rear reservoir had come down again.

Problem is I dont know where the leak is, I can see anywhere were there is fluid leaking.

However if I look at the brake booster, I can see that the paint has been eaten away by brake fluid directly below the master cylinder... I can spot any fresh brake fluid but that's the closest thing to a leak I managed to find on the car.


Anybody knows what it could be ?

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

If it is a standard transmission, I'd say it is going out the clutch master/slave cylinders.
It it's not, I'd say it's going into the brake booster.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

It's an auto...

So the brake master cylinder would be bad ???

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

That's my hypothesis. You could probably confirm it by removing the master cylinder and seeing if there is any evidence of fluid on the back side of it.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

That's a good thing. Replacement rotor fluid is extremely hard to come by!!!

I meant the calipers

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

a wise guy.....knuck nuck nuck!

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

There is usually a small "weep" hole near the rear flange of the master cylinder. It sounds like you have had a leak there, which would mean that the rear seal in the MC has probably failed. Leakage into the booster is a definite possibility.

I have a parts car that had awesome brakes before I took the motor out. Should I try to replace the seal in the bad one or jus simply replace the master cylinder since I already got it.

This I should swap the booster as well ?

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

I would swap the entire master cylinder. It's too early to tell about the booster. You might be able to just clean it out if it is full of fluid.

You will want to suck the brake fluid out of the booster if it is in there....

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

How ?

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

Something like this from Harbor Freight or Northern, or where ever....

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=3878&CategoryName=&SubCategoryName=

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I want to thank you guyz for helping me out. I finaly got around to pulling the master cylinder last weekend and sure enought the booster was full of fluid. I used the exact pump that was recommended to suck it all out. I also decided to go with a new master cylinder since they are only 50$ news.

__________________
1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

You may have noticed an "o" ring between MC and booster, more than likely source of leak.

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83 SD

84 CD