ABS but front wheel locks up

[c.morewood]

I cleaned and bled the brakes for the impending MOT retest but noticed during trying to bed the brake pads in again, that the n/s front will lock up under heavy braking. I have ABS and that shouldn't happen.. the ABS light goes out as normal on startup and doesn't reappear.. any ideas?

[DickieG]

Is this at very slow speed?

[c.morewood]

From about 20-25mph Dickie..No Lexia faults either.

[Stickyfinger]

Sticking slide bolt or miss placed pads ?.both sides or one ?

[citroenxm]

Ive known of this problem.. tevis ecus are known to have some issues but not many..

But the car i had it on i didnt discover the issue till it was too late and id sold the car.

It can be either the ecu or valve block.. theres a bit of good news.. the ecu can be removed from the valve block on its own.. two bolts and a clip on the connector.. however the relay/engine fuse box is in the way of getting at the bolts for the ecu...

[c.morewood]

Slide bolts were well greased today, not sure how you could misplace the pads other than putting them in at an angle and that would show up in uneven wear.. they looked fine today.
Hadn't heard about the ecu problem before, thanks Paul. I suppose there's no way of testing it other than replacing it? And the same with the valve block? Lexia certainly didn't show any faults, current or historical.

[chinkostu]

The little notch on the pad is lined up with the piston right? I misaligned mine and it make the brakes stick on

[citroenxm]

Yes chris...

When your me though it dont cost any thing except time.. this could be your lucky night. I can send you a block and ecu if you want for you to try.. if it works you can then decide what its worth to you??

I won't be able to send anything now till next week. I wont be back to the farm to at least monday now after the northen rally..

[citroenxm]

Lets have a think about this... why would it be pads??

If the wheel locks.. the drive shaft stops.. this then the ecu will detect.. what happens when an abs ecu kicks in? You feel a pulse and noise through the pedal! Im sure chris would feel this if the abs was working correctly.

So no. I dont think chris needs to even consider pads.. its a valve block or ecu problem. And cant be a senor problem because A they pass the resistance test .. b if they were too far away from the cv joint teeth the light would show

[DickieG]

If you have access to Lexia or other diagnostic equipment it'd be worthwhile observing the speed detected by each of the wheel sensors whilst the car is being driven as a starting point.

[c.morewood]

Yes please Paul, When you can .. I have till the 10th till the MOT runs out.. but have a retest on Thu. I'm in the dark with ABS as I've never had problems apart from the sensors.
I'll give the Lexia another go tomorrow and observe the speeds.
Thanks for all the advice.

[chinkostu]

The question is, did the ABS work properly beforehand?

The reason i mentioned the pads is because i buggered mine and they locked on, hard. So the abs could be kicking in but the piston can't retract as the pads jammed

[c.morewood]

I'm pretty sure it was working earlier in the year when it snowed for a couple of days.. I had an ABS fault caused by a sensor due to rust in the reluctor ring back in Feb.. no probs since then.

[Stickyfinger]

Handbrake cable incorrectly adjusted resulting in tighter pull one side ?.......just plucking out easy things to check

[c.morewood]

Nope did that yesterday as well.. there new Mot's are a bugger they find every little fault as I'm sure a lot of you will find out as the new rolling and vibrating computerised test beds are introduced.
Anyway I don't think any handbrake imbalance wouldn't stop the ABS from working..