I was bleeding the front o/s caliper yesterday and noticed the pedal goes right to the floor with the bleed nipple open. Is this normal?

If it is, how would the opposite brake work if i ruptured a brake pipe, as the pedal would go to the floor.

My mate reckons the pedal should only go half way down when bleeding, and i have a fault in the master cylinder.

Anyone know please?

Cheers,

yeah that is normal because there is no resistance on the pedal.

Ok, so how does the dual circuit braking work then?

I think its a diagonal system on the Z? So if i lost fluid from o/s front , n/s front and o/s rear should still work. But if the pedal goes to the floor....how can it?

Does anyone know? Or am i talking bo11ox, i cant work it out lol

The master cylinder can always be fully depressed if any of the bleed valves are undone.

 

In the event of total hydraulic-brake failure, you have the handbrake to slow and ultimately stop the car.

 

Go buy yourself a bag of salt, sounds like it'll come in handy each time your mate tries to diagnose a problem with your car.

 

hope this helps

Simon.

PMSL that is CLASS :rofl::rofl::rofl:

So its not got dual circuit brakes?? I cant believe that.

The mate in question is an experienced mechanic btw lol, and has a great reputation locally, doesnt work on Zeds tho! I dont get that, do i make him eat the salt or throw it at him?

He said he works on cars where the pedal only goes half way down when bleeding brakes, which makes sense but ive never heard of it before.

So are you saying the Z only has single circuit brakes? I thought that went out in the 70's.

Cheers,

Trev, You are correct in stating that the zed has twin circuit brakes but your not understanding it correctly. Firstly however I have never seen a car where the pedal only goes half way down when bleeding? not saying they dont exist but I have never seen one.

 

The duel circuit refer`s to the way the master cylinder operates, and how it is fed by the resevoir that has two sections, the opposite brake outputs are designed primarily if there is a failure in the master cylinder or a loss of fluid in one section of the cylinder.

 

If a hose is lost at any corner of the car it will always cause the pedal to go to the floor, is is not designed to prevent that, by spliting the brake circuits across the corners of the car it aids braking stability.

 

Jeff TT

Thanks Jeff,

I thought it was something like that!

But if a brake hose went i thought it would only empty one section of the master cylinder, so you'd still have 2 wheels braking on the other section. Seems a bit pointless if it wont do that!

I think the car with the halfway down pedal was French , Renault or citroen.

Cheers,

ooh, lots of different ideas!!

 

ok, firstly: the zed (as all modern cars) does have dual circuit brakes, & it is there as a safety feature.

 

using the handbrake is of course another idea, but not everyone will think of that, & it will almost certainly lock the rear wheels causing skidding & poss loss of control of the car.

 

it IS there if there is a failure in 1 of the lines. BUT it wont stop half way!!!

 

the inside of the master cyl contains 2 pistons in line so that the brake pressure will go to each circuit. under normal oporation, the pressure will compress in both lines. failure of 1 circuit will cause that piston to bottom out before the other starts to move & compress the next circuit.

 

so rather than the pedal moving half way, its more like 90% of the way.

Cheers mate