Brake pedal weirdness - Unwelcome ABS?

Right,

I had some work done on my car by a garage not last Thursday (not the one just gone) they:

1) Replaced a track rod end that had failed
2) Replaced a CV Boot Gaiter (or whatever it's called)
3) Unblocked the drainage holes (Plenum chamber I think it's called?)
4) Tracked the car
5) ATTEMPTED to replace a front wheel bearing, but failed because the bolts are seized in and didn't want to continue before having replacement bolts in.

HOWEVER

Upon driving out of the garage, and several times since (about 1 in every 20 times that I apply the brakes) the brakes go weird on me. The brakes WORK, but there is a grumbling noise and some vibration/feedback through the pedal and it feels and sounds not dissimilar to when ABS kicks in.

But it generally does it only under light braking - coming to a gradual stop at some traffic lights - under no circumstances would it be cause for the ABS to even THINK about kicking in.

I don't know whethr it is the ABS... but I'm wondering if anyone here could shed some light. It's brakes, so I'm concerned about it. I've done 400 miles since I've had it back because i've had to use it, and the brakes haven't failed, but it's rather disconcerting!

Any info/advice/help would be greatly appreciated! It's ONLY done it since I got it back from the garage.

Thanks

By the way it's an R reg (1997) A4 Saloon 1.9 TDi 110. 119k miles on the clock, and otherwise works great!

When doing the CV boot the sensor has moved or the teeth on the CV have become dirty and this reduces the sensor sensitivity so it is dropping out and the ABS ECU thinks that wheel is locking.

Ok - thanks. Is this is a common problem when doing this job? Is it easy to fix, and is it a fault of the garage that did the work?

Thanks for the quick reply - appreciate it.

They need to take the sensor out, blast brake cleaner in there whilst spinning the wheel and then blow clear with compressed air. If that doesn’t cure it, deeper investigation will be required.

OK - Thanks.

Presumably this is caused by them when they did the work and as such should carry that work out for free?

Is this common when doing the CV boot?

Thanks again Crasher.

Not common but it can happen.

I phoned the garage and am to drop the car off on Wednesday.

They said that I wont have to pay if the problem is a result of their actions.

I quoted reply #2 but he said that if it's not because of their actions I'll have to pay.

The sceptical side of me says that they are going to say it's nothing to do with them and charge me the earth to fix it.

I've phoned the national service network to get a quote for the wheel bearing, at least if I get work done through one of their garages it's guaranteed for a year and I deal with NSN and NOT the garage at fault - decidedly less awkward than phoning and saying "Yes, hello. I think you broke something on my car." I never like making those kinds of phone calls...

Dropped it off this morning - fingers crossed they wont charge me.

Well... They didn't charge me... BUT

They said they cleaned the ABS sensor and then road tested it BUT THE PROBLEM IS STILL THERE (Angry) :zx11:

The ABS speed sensor readings need to be observed in Measuring Blocks 08 to see which one is dropping out early and then the attention can be paid to that sensor.