Wabco ABS problem - intermittent hard pedal

Can anyone help?
Just bought a 2000 W 1.8 XEI 5 door Freelander with knowledge of it having a problem (it was cheap); intermittently, there's no brakes!

I was led to belive that it was the ABS modulator so bought a second hand one from Equicar and fitted it - only to find out it performs exactly the same way. I don't want to replace everything till it does work so here goes....

Every now and again, the brakes seem to fail - the brake pedal doesn't depress in the usual way (its hard and doesn't have much travel) and the're virtually no braking (although theres a small amount). There's also a sound which is similar to metal to metal contact of brakes.

I've checked that the servo works (by evacuating all the air with the engine off then starting the engine - the pedal sinks as the vacuum builds
The 3-amigos aren't present - although they do light up in the normal pre-check fashoin.
The ABS light goes out at 5-8MPH and stays out
The ABS functions properly most of the time (tried braking really hard in gravel and the pedal pulsates properly)
Diagnostics testing shows that the replaced ABS unit pump and solenoids work when triggerd.
Same testing shows that the speedo can be set to 100 & 200KMH by laptop with only the ignition on
Live data shows there's a signal going to the wheel sensors - but no signal coming back
A brake line to the ABS pump/modulator has been replaced at some time and I've traced it back to ensure it does go to the right (i.e correct) rear wheel
Live data can't pick up road speed.
At one stage, the speedo went dead (fixed by replacing a fuse)
The Auxiliary power point fuse kept popping till I disconnected it at the rear of the handbrake console (not related to above - I think)
We THINK the problem tends to occurr more often above about 20MPH
The brakes have been bled using a vacuum at the caliper/cylinder bleed nipple
Both rear wheel cylinders were leaking badly so were replaced with Lockheed items
A quick look at the ABS rings on the front driveshafts show them to be catching somewhere and becoming shiny in places - although not the full 360 degrees indicating perhaps some rust distorting them.
Similarly, the ABS sensors have begun to be worn away at their tips.

Can anyone help with a few questions;
1 Has anyone got a ready made answer (other then sell the car on)
2 Is there a free link to a URL for the ABS wiring diagram for this type of Freelander
3 Can anyone tell me if there's a primary wheel speed sensor (most german cars take it from the NSF)

Thanks - & you know if I coud help you out, I would!

Hi,i'm just wondering if you managed to track down your intermittant hard pedal problem coz i seem to have the same thing,any clues would be great thanks.

Cubanreef said:

There's also a sound which is similar to metal to metal contact of brakes.

Live data shows there's a signal going to the wheel sensors - but no signal coming back

Live data can't pick up road speed.

A quick look at the ABS rings on the front driveshafts show them to be catching somewhere and becoming shiny in places - although not the full 360 degrees indicating perhaps some rust distorting them.

Similarly, the ABS sensors have begun to be worn away at their tips.

Click to expand...

I think you might be close to answering your own problem here.

metal to metal sound like brakes ? or more like abs sensor to stator ring ?

no road speed data coming back? vehicle abs won't know how fast wheel is rotating so will assume wheel is stationary and release brake to that wheel.

if the abs rings are shiny in places indicating catching, something is wrong. abs sensors should never actually touch the ring. close, but never touching.

Like wise, the abs sensors should never wear away as they shouldn't be touching the stator ring. again something is wrong.

It might be worth removing and refitting the abs sensors first, but I certainly wouldn't trust them on the basis of what you have told us in your post.

The abs ecu can only act on the information it receives from the four wheel sensors. If that information is in anyway incorrect, then the decisions the ecu makes about releasing the brakes will be wrong.

Before you go any further with your investigations, I would deal with the abs sensor & stator ring problem first. Once you are happy that this part of the braking system is correct, then begin to look at other issues.

Good luck, all advice at your own risk etc etc