Bad Brake Master Cylinder?

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?

How many miles on the truck and how long since you flushed the fluid?
Mike

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

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

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!

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,

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.

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.

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

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.

quote:

ORIGINAL: DISCOHAITI

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.

First check that play in the bearing is the problem - jack up the car and grip the road wheel top and bottom and rock the wheel - always use axle stands, never try this on ust a jack alone.  If there's a lot of play then adjust the bearings.  If there's only a tiny amount of play you'll probably be wasting your time adjusting them.

To do it according to the manual you'll need a dial test gauge to measure the tiny amount of slack required in the bearing for normal operation.  However, I did mine by feel... essentially, wind the inner hub nut up as tight as you can BY HAND (under no circs use any sort of tool or you risk killing the bearing) and then back the nut off approx. one quarter of a turn.  Check for play in the hub by giving it a good wiggle by hand - you should just about be able to feel it move - if you can see it moving more than a fraction of a milimeter then it's too loose.  If the inner nut is too tight, once it's at running temp., the outer race of the bearing can cause the inner race to turn on the stub axle and you'll need a new bearing and stub axle to fix the problem.

Always use a new locking washer!

Now comes the tricky part you have to do the outer hub nut (or locking nut) up to the specified torque without allowing the inner nut to turn.  I've found it's a lot easier with two people, one holding the inner nut in position with a screwdriver wedged against it while the other torques up the nut.  If the inner nut moves, start over.

That's pretty much it - don't forget to check the play in the bearing once the road wheel is back on, if there is none there, you'll have to start over.  Likewise, if there's too much play and the roadwheel feels slack, have another go making the inner nut a little tighter than before.

Cheers,

this is a common problem,it is normal for that year,no fix from landrover yet