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Old 07-14-2008, 05:46 PM
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Join Date: Jul 2008
Location: Land O' Lakes Fl.
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'78 300 D brake issues

Howdy all,
I'm reletavely new here and I am having an issue with my brakes.
I was driving the car home tonght from work and I noticed that the brakes were taking more pedal travel than usual to stop the car.
It kept getting worse the closer I got to home.
By the time I pulled into the driveway I only had rear brakes.
I opened the hood expecting to see a near empty resivoir, but it was nearly full still.
I peeked under the car expecting to a leaking hose or caliper or something, dry as a bone.
Same thing with the rears.
I got back in the car and I found that I could pump the pedal and get better pressure.
I left it alone for a bit and tried the pedal again and it seemed to stay up.
It's acting really wierd.
I'm wondering if one of the seals in the master cylinder took a dump and isn't generating any pressure in the front brake circuit.
Is this possible with these cars?
I'm new to Mercedes Benzes but not to older cars.
Usually when I have an issue like this there's an obvious reason, like a leaky hose or something.
Am I missing something?
Help!!!

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  #2  
Old 07-14-2008, 09:24 PM
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Join Date: Jul 2007
Location: USA
Posts: 2,156
Sounds like you got a vacuum leak. YOur master clyinder is either leaking( bad seals) or your booster is going.

Have you tried rebleeding the brakes to get out any air in the system?
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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)
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  #3  
Old 07-14-2008, 09:32 PM
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Location: Mount Holly, NC
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wow way to cover all the bases with a response...
were the rear brakes locking up when you pressed the pedal? it really sounds like the master cylinder is hosed, but it could be the front reservoir has gone dry. are you SURE the entire reservoir is full? there is a partition in the thing, sometimes hard to see if it's empty on one tank.
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  #4  
Old 07-14-2008, 10:31 PM
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Quote:
Originally Posted by vstech View Post
wow way to cover all the bases with a response...
were the rear brakes locking up when you pressed the pedal? it really sounds like the master cylinder is hosed, but it could be the front reservoir has gone dry. are you SURE the entire reservoir is full? there is a partition in the thing, sometimes hard to see if it's empty on one tank.

Wouldnt his brake fluid level warning light be on then?
__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)
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  #5  
Old 07-16-2008, 04:55 PM
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Join Date: Jul 2008
Location: Land O' Lakes Fl.
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Quote:
Originally Posted by vstech View Post
wow way to cover all the bases with a response...
were the rear brakes locking up when you pressed the pedal? it really sounds like the master cylinder is hosed, but it could be the front reservoir has gone dry. are you SURE the entire reservoir is full? there is a partition in the thing, sometimes hard to see if it's empty on one tank.
Thanks for the replies, guys.
yeah, the rears were locking up.
I think it's the M/C too because the brake fluid is disappearing and I can't find a leak.
The whole resivoir was full too.
That only leaves on place for it to go, into the booster
I'm gonna check that next.

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