MQ Disappearing Brakes?

[johnnno004]

Hey everyone, Ive got a 84' MQ Shorty SD33T and having problems with the brakes. While the cars off if I pump the brake pedal there is solid compression, but when the car is on the only way to get brakes is to pump the pedal a few times to make compression then there is just enough braking power to slow the car down, but if I dont use the breaks for about 4-5 seconds there becomes no compression again. If anyone can help, much appreciated.

[tehekho]

can yoo pull the car up with a single press of the brake pedal, or does it just feel more soliderer with the engine off?

Are they a drum brake rear? Sounds like your rear shoes need adjustment/replacing, could be a naff rear slave. Drums should auto adjust, but as they age, the ratchet system in them starts to fail, and if you have a slight fluid leak as well then that just gums everything up and it's not very fun any more.

Drums are easy but fiddly to work with.

[johnnno004]

Front Disc, Rear drum. A single push of the pedal hits the firewall but 3 or 4 pumps and i get some breaks back for a couple of seconds then looses compression again. The brakes used to be fantastic but havn't driven it much in the last few months and now the brakes have this problem..

[xXrhodieXx]

I had a similar problem with mine, i dumped all the brake fluid, done a full line bleed, all good now.

[howsie]

If your pumping it and regaining pressure then its one of 2 things air in the line so bleed your brakes or your brake master cylinder is gone

[Nat84]

sounds like your rear brakes need adjusting or your muster cyclinder is no good

[V8Patrol]

one of two things........

1/
Leaking master cylinder
to test.....
start engine
pump brakes till pressure is obtained
hold brake down as if heavy braking

if brake pedal slowly falls to the floor - replace master cylinder



2/
Rear brake adjustment
to test
jack up rear of vehicle so both rear wheels are off the deck
get an assistant to apply the brakes (no pumping) & hold the pedal down
try and 'spin' the rear wheels by hand (they shouldnt move)

if they move..... give a pump on the pedal and repeat the spin test

If it takes several pumps to stop the wheels from turning then adjust the rear brakes..... (done with a screwdriver through the slot in the brake backing plate)