Bad Brake Master Cylinder?

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Bad Brake Master Cylinder?

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Bad Brake Master Cylinder? - 7/11/2007 7:55:59 AM

larry99discoI

Posts: 2
Joined: 7/11/2007
Status: offline

When I press the brake pedal on my 99 DiscoI it goes nearly to the floor. One pump of the pedal firms them up for good stopping. The rotors and pads are fairly new, and the brake fluid is full. My mechanic say's the "one pump" symptom most probably means I have a bad Master Cylinder. Does this sound right? If so, can a novice mechanic like me replace/rebuild the master cylinder? Where can I find a rebuilt master cylinder? I see Atlantic British has a new master cylinder for $190. Any other good sources?

Post #: 1

RE: Bad Brake Master Cylinder? - 7/11/2007 9:53:29 AM

Disco Mike

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Joined: 4/27/2006
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How many miles on the truck and how long since you flushed the fluid?
Mike

(in reply to larry99discoI)

Post #: 2

RE: Bad Brake Master Cylinder? - 7/17/2007 9:50:29 AM

larry99discoI

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Joined: 7/11/2007
Status: offline

90,000 mi, don't know if they have ever been flushed. Thanks

(in reply to Disco Mike)

Post #: 3

RE: Bad Brake Master Cylinder? - 7/17/2007 1:15:12 PM

Disco Mike

Posts: 10530
Joined: 4/27/2006
Status: offline

Start with a full brake flush and remember in the future, change the fluid in a Rover about every 20,000 miles.
If flushing doesn't work then change out the master cylinder also.
Check with Rover Connection and DAP for kits or new cylinders.
Mike

(in reply to larry99discoI)

Post #: 4

RE: Bad Brake Master Cylinder? - 7/22/2007 5:41:39 PM

dwilson1984

Posts: 6
Joined: 7/22/2007
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I'm having the same issue, I was driving in downtown houston and make home and when I was about to stop under my covered parking spot my trunk would not stop!!!!!!!!!!!!!!!!! Fluid is there!

(in reply to Disco Mike)

Post #: 5

RE: Bad Brake Master Cylinder? - 7/23/2007 5:01:18 AM

Adz

Posts: 317
Joined: 11/19/2006
Status: offline

Disco 1 uses the same hubs as the Defender - could be the bearings need adjusting. If they're too loose the pistons in the caliper get pushed back more than normal due to the extra movement in the hub - thus, first press of the pedal and it'll go a lot lower than normal, second press and the pistons have moved back out and normal braking is restored. Over the course of a few miles and they'll get moved back in again and the process is repeated.

If it's air or water in the brakes, releasing the pedal and repressing it after a few seconds, with the engine running, whether the car is in motion or not and you'll get the same symptom of the pedal going lower than normal. If it's the hubs, with the engine running but the car stationary and the pedal will be normal until you drive off.

Hope that helps,

(in reply to dwilson1984)

Post #: 6

RE: Bad Brake Master Cylinder? - 7/24/2007 5:15:29 PM

chizel

Posts: 4
Joined: 7/24/2007
Status: offline

You will not normally see the brake fluid leaking out externally of the brake master cylinder or from the wheel areas when this pedal softness occurs, so fluid level alone isn't an indication of a good or bad brake master cylinder. The fluid will usually not be low or in need of topping off…remember the leak is internal and the brake fluid is leaking past internal O-rings, so an obvious external sign that the master cylinder is "bad" is usually not existent.

(in reply to Adz)

Post #: 7

RE: Bad Brake Master Cylinder? - 8/3/2007 8:31:21 AM

DISCOHAITI

Posts: 8
Joined: 5/4/2007
Status: offline

Adz - Is adjusting the bearings an esay task? One that can be done in the driveway? I think this may be the cause of a steering wheel shake when I brake. I've changed everything there is to change but have the same problem. Also my front left pads wear quicker than the other side.

(in reply to Adz)

Post #: 8

RE: Bad Brake Master Cylinder? - 8/5/2007 6:33:42 PM

sharonsbaby

Posts: 3
Joined: 8/5/2007
Status: offline

i had same problem and replaced master cylinder. now, the pedal is soft and although it does not go to the floor, is takes entirely too long to stop the car. if an emergency happened i might be in trouble

(in reply to DISCOHAITI)

Post #: 9

RE: Bad Brake Master Cylinder? - 8/5/2007 6:34:52 PM

sharonsbaby

Posts: 3
Joined: 8/5/2007
Status: offline

is there something else i can do to fix this problem? i have bled the brakes twice with no air coming out and i bench bled the master cylinder before i put it in.

(in reply to sharonsbaby)

Post #: 10