Brake judder at low speed 325i Touring

[M3Macao]

I wonder if someone can shed a little light on this problem. Ive noticed that when im approaching a junction at low speed and start to turn the steering to the right the brakes judder and feel like they are coming off and on. Ive been working through a list of possibles to try and narrow it down. Ive replaced the lower control arms , bushes and arb links. Ive taken the ABS sensors out and cleaned them up and its still doing it.

Im thinking ABS now either sensors or pump..any ideas??

Cheers in advance!!

Andy.

[M3Macao]

bump...

[murran]

sounds like an abs problem to me, like on earlier audi systems where the clearances are too big between the abs sensors and the rings on the driveshafts. the abs chatters/cuts in just as you brake just before the car stops??

best to get a multi meter check all the sensors have the correct resistance thru them at the relevant wires at the control unit.
if they check out, then get a scope and connect it to the signal wire for 1 of the sensors, jack the car up then spin that wheel and look at the wave form/strength. do all wheels/sensors. if one is different from the others then this is probably the problem.
adjust the clearance on the sensor, see if it alters the wave form. if not it might be a corroded wire causing higher resistance, check this with the multi meter, checking the continuity (ohms).
mr mooooore is the one to ask which wires are what and what resistances you should see to do these checks.... or if you can read wiring diagrams then put "e30 wiring diagrams" in google and find some.

sounds long winded i know but it sounds like youve tried everything else.........

[BadDave]

Just a thought
Are the front ABS rings full of crud etc?
If so, try giving them a clear out.
The sensor/ABS ecu could be "sensing" that the wheel has locked up momenteraly

Failing that,try and attract brianmooore's attention for some more in depth analysis


HTH

[murran]

mmmm could be a corroded or cracked ring (oooo err.)

[M3Macao]

Thanks Murran and BadDave!!
I think ive definately narrowed it down to the ABS..problem is which part! Ill try everything you suggested Murran..it does sound long winded but ive got a bit of time on my hands at the mo..ill just have to scrounge a multimeter! I took each sensor out today and cleaned them up as they were covered in crud..still the same. Ill swap them all over with a working set i bought from ChrisW and see what happens. Its MOT time next month and ive been working my way through a huge list of jobs..just need to get this one sorted and hopefully thatll be it! Fatefull last words..!

Murran..where would i find the corroded or possibly cracked ring? Inside caliper?

[BadDave]

where would i find the corroded or possibly cracked ring? Inside caliper?

The problematic ones are usually on the front
They are on the front wheel bearing/hubs
Only way to really check them, is to remove them(36mm socket) and have a good look/clean them up

[Nelly]

Might be worth while replacing both front wheel bearings, £28ish each from ecp but be sure to get the abs ones - at least this way you'll have 2x new bearings up front with completely corrosion free abs toothed rings.

[M3Macao]

Thanks for all your suggestions guys..the problem has now been solved!! I stripped it all down today and cleaned everything up. I traced the fault to the N/S/F sensor so replaced that and the O/S/F sensor as well. The car now brakes perfectly with no juddering!!

I really like E30's they are a doddle to work on and you only need a handfull of tools and a can of WD40!!