Brake pedal travel

[Snap-on]

Hey peoples,
Just replaced the brake master cylinder today on my VH. The front discs are fine, new pads, rear drums are fine and has new drum cylinders. I bled the master cylinder before installation and then bled the system at each corner, two times.
The problem I have is that the pedal travel is still about half way ie: You need to depress the brake pedal 50% of the way to the floor until the car starts to pull up.
Question is: Is this normal with your cars? Or is my VH in need of more repairs?
Cheers, Deano

[Lewie]

Did you replace the brake master cylinder with a new identical unit? Eg same diameter? Did you do anything to the booster or lines? I assume you're not loosing any fluid.

[Snap-on]

yep identical pbr replacement part, didn't even touch the booster lines and its holding fluid quite well. That's why I can't figure it out!

[drippy]

did you correctly prime the master cylinder, if you dont i do believe they get an air lock that you cant get out unless u take it out and do it on the bench

[Snap-on]

Yep sure did

I bled the master cylinder before installation and then bled the system at each corner, two times.

[leigh 7005]

probarly the booster the are pices of sh*# ive changed about 6 second hand ones and they are all the same leaking is it making a sucking noise?

[Street racer]

Hey the best thing for you would be to go and see a mechanic person and ask them,becuase if you trying to fix that by yourself something mite go wrong.

[Snap-on]

probarly the booster the are pices of sh*# ive changed about 6 second hand ones and they are all the same leaking is it making a sucking noise?

Hmmm yeah im thinking this aswell cos the booster is rusty and old lol

And yeah I was thinking about taking it to one those things, what do you call them - McKennocks?

Any one else had this issue?

[ari666]

soz for the late post, but TBH is sounds like your system still isnt bled properley. if your boosted is naff itll be really hard to depress the pedal, not free-paly for half.

i dont mean to be a pain and you can ignore my advice, but you MUST start from the rear passenger side wheel first, as its the furtherst from the master cylinder. i went through this crap too, tried three times and no good, then one day it just worked.

so start with the rear passenger side, stick a clear hose onto the bleed valve and lift it above the height of the master cylinder. pump your pedal a few times as normal (while the engine is running) then get your mate to release the valve quickly while you are depressed., it takes a few goes to make sure there are no bubbles in the clear hose you ran, but when you are a million per cent sure there are no bubbles, move on to the rear drivers side.

itll waste a bunch of fluid so be ready for that.

soz, but i am pretty sure if you give it one more go you will hit it

[immortality]

i agree with ari666, you need to bleed the system again. a faulty booster results in a hard pedal (i have lots of experience with this particular fault )

the other option is to take it to a brake shop and have it pressure bled. might cost a little bit but guarantied to sort the problem.

for the next time you replace a MC, reconnect the brake line but leave em a little loose, then go to each caliper and squeeze the piston back in a little, this way it removes any air in the brake lines at the MC. wrap the whole area in rags to prevent getting it on the paint work. then tighten the fittings properly

[Commydoor]

sounds to me like they gave you the incorrect size rear wheel cylinders (larger bore diameter)

[ari666]

for the next time you replace a MC, reconnect the brake line but leave em a little loose, then go to each caliper and squeeze the piston back in a little, this way it removes any air in the brake lines at the MC.

yet another really good idea im gonna use that. cant beleive i had never heard of it b4.

[leigh 7005]

so if the booster is stuffed itll be stiff i thought if the booster is stuffed youll hear a sucking noise corect me if im wrong?

[codfishface]

Correct on both counts.

A stuffed diaphragm in the booster will make a sucking noise and will affect the boosters ability to assist the master cylinder.

[Not_An_Abba_Fan]

You shouldn't pump up the pedal when bleeding, all that does is aerate the brake fluid.

The best method is to leave the engine off, open the bleeder, push the pedal down, close the bleeder. Do that until there are no bubbles coming out. You don't need to raise the clear hose above the master cylinder either.

Another thing, did you reset the brake switch on the side of the master cylinder? Undo it until you hear a click then do it up again.

[Snap-on]

Thanks for all your input fellas! I'm gonna bleed the system again to see if it fixes the problem.

Another thing, did you reset the brake switch on the side of the master cylinder? Undo it until you hear a click then do it up again.

What is the brake switch - the electrical plug? What will re setting it do?

[Not_An_Abba_Fan]

When the pedal goes too far it activates a brake warning light. There is a pin in the switch that goes into a groove in the piston and locks it about half way in the master cylinder. Undoing it until you hear the click will let the piston come back to it's proper position. Sometimes that is what causes a low pedal.

[leigh 7005]

When the pedal goes too far it activates a brake warning light. There is a pin in the switch that goes into a groove in the piston and locks it about half way in the master cylinder. Undoing it until you hear the click will let the piston come back to it's proper position. Sometimes that is what causes a low pedal.

ill try that 2 thanks

[Snap-on]

hmmm very interesting. I will have to try this too.