Brake pedal pulse

[Johnny2R]

Take a look at the suggestions on this thread: http://www.the75andztclub.co.uk/foru...d.php?t=207353. Obviously in your case it's not a replacement of a sensor which has caused the issue but something else, but it sounds like the actual mechanism is the same, i.e., a sensor misreading because of a gap.

[Richcl]

I'm with warped discs, the disc pushes the pistons in and out as it spins and you feel this through the brake pedal.

[Mike Noc]

Originally Posted by Johnny2R

Do the symptoms you've been getting sound the same as what I described in another thread as "when I brake (from any speed), just as the car is about to come to a halt, I feel that momentary rapid pulsing judder in the brake pedal when the ABS kicks in"?

Johnny I had the same after changing a rear ABS sensor. The air gap was slightly too big between the sensor and reluctor ring. You can check the sensors and reluctor rings with a multimeter, and on mine the sensor would pick up every reluctor segment until the wheel slowed down, and then it would miss the odd segment.

I assumed the system read this as a wheel locking and so activated the ABS.

I don't know if that would be picked up by a T4 or not, as it isn't registering as a fault as such, just the ABS system activating?

The difference I've seen between a warped disc and the ABS activating is that warped discs will pulse the pedal at all speeds, and the speed of the pulse is directly related to road speed, which doesn't sound like what you are experiencing.

[BigRuss]

T4 will see it if you road test the car whilst looking at the live data which shows each wheel speed

The culprit(s) will show up with a lower speed than the others when driven on a straight even road.

Note this doesn't apply if there are different sized tyres fitted than the others as the circumference of the tyre is different this can cause the abs system to operate all the time or at low speeds too

Russ

[maciejk]

Hi, I also got a pulsing pedal not every time but only at around (6mph) this started happening after changing the front driver abs sensor, abs light was on, cruise control still not working, thought it would fix the problem (maybe the pedal sensors are out of place haven't checked) the surface wasn't slippery and the wheels did not lock up, but the pedal starts pulsing, not a disc issue i'm sure of it, is this normal? from time to time that ABS light stays for a second or two after I start the engine but goes out

[trikey]

Originally Posted by maciejk

Hi, I also got a pulsing pedal only at around (6mph) this started happening after changing the front driver abs sensor, abs light was on, cruise control still not working, thought it would fix the problem (maybe the pedal sensors are out of place haven't checked) the surface wasn't slippery and the wheels did not lock up, but the pedal starts pulsing, not a disc issue i'm sure of it, is this normal? from time to time that ABS light stays for a second or two after I start the engine but goes out

Rear wheel bearings can cause this.

[maciejk]

but why right after the front sensor has been replaced? this didn't happen before when the abs light wasn't coming on, bearings don't make a noise all quiet, u mean the magnetic ring maybe?

[Jakg]

Bearings have the "magentic ring" (reductor ring?) built in.

[DMGRS]

Originally Posted by maciejk

but why right after the front sensor has been replaced? this didn't happen before when the abs light wasn't coming on, bearings don't make a noise all quiet, u mean the magnetic ring maybe?

The sensor isn't sat far enough in it's mounting hole - usually caused by rust build up on the hub.
Remove the sensor, clean everything up, and refit - it should be OK then.

[trikey]

Originally Posted by maciejk

but why right after the front sensor has been replaced? this didn't happen before when the abs light wasn't coming on, bearings don't make a noise all quiet, u mean the magnetic ring maybe?

I have changed a few that appear to be fine, no noise, no wear, just doesn't trigger the abs properly.