Outer Limits 4x4 Board

hello all
i am having a problem with my vacuum brakes.
i had a new master brake cylinder put on my MQ 1984 patrol
and when i picked it up ,the mechanic said i needed a new
vacuum booster or the new brake master cylinder was faulty.
when i put my foot on the pedal with the motor off ,there is plenty
of backpressure there,
but when the motor is running , i have to pump the brake pedal
to get it hard and then it slowly goes to the floor.

your input would be greatly apreciated as this is my first 4wheel drive.

thanks again

ron

Petrol or diesel ?????

If its a diesel then you may also have a vacum problem from the pump which is located on the back of the alternator.
To test this let the engine idle and place your foot on the brake pedel as if you were stopped at a set of traffic lights. If the pedel slowly falls to the floor then its the master cylinder thats stuffed..... BUT if it falls slowly and once its near the floor "pulses" and comes back up a few milimetres at the pedel you have both a faulty master cylinder and a vacum problem at the pump.

Standard test for any vacum setup is..... ( petrol & diesel )
Let the engine idle and place your foot on the brake pedel as if you were stopped at a set of traffic lights. If the pedel slowly falls to the floor then its the master cylinder thats stuffed. The reason being is that the brake fluid is slowly seeping past the piston in the brake master cylinder and back into the fluid reservoir.

Kingy

hi

its a petrol p 40 on lpg

if i pump the pedal up it goes dopwn slowly on idle

thanks again

ron

If the brake fluid isnt dripping on the ground at the wheels .... this means that its definately the master cylinder thats history.

Kingy

hi
the master cylinder is brand new.
its been in for 1 week.
no fluid leaks.

thanks

ron

ron wrote:hi
the master cylinder is brand new.
its been in for 1 week.
no fluid leaks.

thanks

ron

Genuine or aftermarket ??????

I'd be taking it back !

aftermarket?
bought it through aussie auto.
couldnt get a genuine 1.

cost me $90 to get it fitted,
because the gas convertor had to get taken off

thanks

ron

ron wrote:when i picked it up ,the mechanic said i needed a new
vacuum booster or the new brake master cylinder was faulty

"the new brake master cylinder was faulty" is my bet

hi

i dont suppose that they will pay for the mechanic??


thanks

ron

If only life was that simple and every-one did the right thing

oh well,

thanks for the help everyone

will talk to them tomorrow and will see what happens


thanks again

ron

hi all

we took the master cylinder off and took it back to aussie auto and they are now sending it to whoever they bought it of for testing.
looks like i will be without wheels for a while

thanks for all your help

ron