Rear brake pressure reduction valve info

Hi,

I won't go into details about why, but slight, slight possibility my brake problems could be affected by the valve which is supposed to reduce brake pressure to the rear wheels under heavy braking.

Some questions on this:

- is there any way to tell conclusively that it has failed (e.g because when it fails it leaks fluid or something)?
- is it realistic that it might have failed in such a way to constantly reduce the pressure?
- or would it just basically have no affect if it failed, i.e as if it was not there so always normal pressure to rear under any circumstances?
- any idea on replacement cost: are we talking silly money?

No time to do lengthy update on on-going brake problems etc. as forum going down in a few minutes!!!!

Cheers,
Pete

[gnhuk]

Pete,

I think that there is a pressure relief valve somewhere though how you'd test it I've no idea - assuming there is a way. My Mondeo got recalled for a replacement of exactly this item and I didn't notice any difference afterwards.

It might be worthwhile seeking out a brake specialist and asking a few questions.......

[Rooster]

They don't have one so it carn't go wrong, got abs instead

Originally Posted by Rooster

They don't have one so it carn't go wrong, got abs instead

ah, if only that were true then it couldn't go wrong ... but no there is one left hand side of engine bay on bulkhead....2 feed lines from abs go into it, 1 for each rear brake, 2 out of it to rear brakes... p/n 30818013, "valve".... although I am more used to vw systems where it is integral with ABS unit hence some of the questions...

Pete

[Rooster]

Why do you think its bust,

I thought that was just a joint so if you were replacing brake pipes you didn't have to run them all way to abs unit

According to haynes it is a pressure reduction valve like old cars would've had which reduces pressure to the rears under heavy braking to prevent the rears locking and keep the bias to the front (where all the effective load/weight is).

I should stress that for my problem it is most likely that this is not at fault, but it might be so I wanted to get a potential idea of what to look for and cost.

My problem is that under anything approaching heavy braking the ABS activates in such a way that the pedal gives and stays like that, i.e the ABS thinks one or more wheels are decelerating too fast and then even when the ABS blocks the brake line or pumps back the fluid then it stays like that. I have disabled the ABS and I can tell that the rears are braking too much with respect to the front.

Now, I think the problem is actually a fricition problem with one or both rear brakes not so much binding all the time but maybe seized caliper guide pins forcing one pad onto the wheel or a knackered caliper or something that causes one or both rears to brake way too much. BTW previous symptoms suggest I also had front brake problems but for sure this problem is now a rear brake problem. I should also point out I strongly suspect the ABS is not at fault.

The brake pressure regulator COULD be at fault on one or both circuits if it was, in some circumstances only maybe, failing to reduce the brake pressure to one or both rear brakes.

Hope it kind of makes sense,
Pete