My continuing braking problems.

Ok, currently got the rear brakes in bits again on my car in an effort to find out why the car keeps failing the MOT on the rear right hand brake efficiency.

So far we have replaced the drums, cylinders and shoes and bled the system right through, and it still failed, so I've decided to investigate the hydraulic system a bit further.

The general flow of fluid to the rear right hand part of the system seems to be very slow. All 3 others get a reasonalbe flow when i use the gunsons easi bleed, but the rear right hand part of the system only gets a slow drip, so I'm sure there's a problem with the hydraulic system.  At the moment I have disconnected the rear brake flexi hoses to see what the flow is like in the system before these, it's better but still poor, even air only trickles through the system to that wheel, but blasts out of the others really freely. I would disconnect the pipes before the compensating valve and check the system here, except i can't get them un-done.  :evil:

The big assumption I'm making here is that the flow to the different parts of the system is supposed to be the same? I want to find if that's a correct assumption to make before i start replacing hydraulic pipes and the compensating valve/master cylinder etc. Anyone know??  :dontknow:

Mike.

Mike,

I would say that the flow should be the same at the rears and same at the fronts - front and rear are probably different.

The flow can only be measured with all other three wheels sealed up - that is to say if both rear pipes are undone the flow might be different to each side.

I presume the compensator is in the correct position?

The flow was measured with the other pipes blocked off, it is substantially less.

The brake compensating valve is pushed all the way in (as per the haynes manual instructions for bleeding the brakes) I'm not convised by this valve, it seems loose and all over the place, but not knowing how it's supposed to feel, i don't really know if this is right or not.

Mike.

could you try bypassing the compensator with a t piece to eliminate it from your flow testing?

I agree with crazyquiff… Flow of brake fluid should definately be the same on either side of the rear axle otherwise the car would pull to one side under braking.

Does it look like the metal pipe and/or flexy pipe on the right hand rear have been changed in the past?

If they have which is likely, it might be that when they were fitted the flared ends of the metal pipe had been made badly on the pipes or got deformed when tightened causing a restriction. Also check to see if the metal pipe is kinked or flattened at all on its bends.
If the flexy pipe looks old it could have broken down internally as Rich said.

I guess it could be the compensating valve but I'd look at the pipes on that side first as they are cheaper. You may need to cut them off if they are too corroded to undo. My compensating valve seems a bit loose and all over the place too. I think this could be normal?

New metal pipes are pretty easy to make up, you just need a pipe flaring/cutting kit, pipe and unions. Just follow the instructions… practice makes perfect when flaring the ends and dont forget to put the unions on before flaring the second end of the pipe! use the old metal pipes to get the correct length of metal pipe and bends where possible.

Cheers,

Ross

Mike did you ever solve this problem ?

If so how ?