Bad vibration occasionally in brakes


#1

I have a 99 VW Beetle. Occasionally, the brake peddle will have a heavy vibration or jumping feeling (almost as if gravel is between the brake pads) while braking. It is not the normal ABS pulsation either. The car does not pull in any direction. The ABS light does not come on everytime it does it and sometimes it comes on and stays on for a while and then goes off when it wants. I have had the rotors and pads replaced and brake system flushed. Prior to this, my daughter did have a rear brake that was down to the metal. The only things left to replace are sensors, calipers, or ABS system itself. Car has to many miles for warrenty work.


#2

The ABS light does not come on everytime it does it

Well clearly it is an ABS related problem. I would suggest getting the codes read, some places like Auto zone and Advanced Auto Parts will do it for free. VW has their own reader that does a lot more than the auto parts stores can, but it should not be needed for your problem.

Post the results back here. Post the actual code (like P0123) not just the description.


#3

some more info is needed.

how long since last brake job?

how many miles?

at the last brake job were the rotor turned (resurfaced) or replaced?

i suspect that if they were resurfaced, they have warped, and you need new rotors.


#4

I would bet that you have brake rotor warp based on the extremely heavy use of your brakes and the condition of previous brake rotors and the need for repeated brake jobs. I have pontificated on this elsewhere, but here’s my view.

Intermittant pedal pulsing that is clearly not ABS related (frequency varies with vehicle speed, while ABS pulsing is always a set frequency) means that you are warping your rotors. This is not often a design flaw, but rather due to excessive use of the brakes. The seemingly intermittant pulsing is caused by having two rotors warped (probably at least the front 2). At times, the position of the high/low spots on the rotor coincide when braking and you get a strong pulsing as both rotors are effectively “synchronized” to pulse at the same time. Other times, after you turn a corner and one wheel rolls out at a different place relative to the warp, the pulsing can almost seem to cancel out.

There is little or nothing that you can do to “fix” rotor warping unless you change your driving habits. You can turn or replace rotors forever, and the warping will return if you drive the same way. I can prove that on any car made.

How to avoid warping:
Avoid coming to a complete stop after hard braking as that causes uneven cooling of the rotor.
Avoid hard braking except in dire emergencies. Plan ahead and slow down early, don’t fly up to a stop and brake hard at the last minute.
Don’t ride your brakes down a hill, use the engine to assist in limiting vehicle speed.

Unless you or your daughter eliminate the cause of the warping, you will spend your paychecks at the garage. My '96 TransAm went 128,000 miles before I had to replace a set of factory pads. Never had a warped rotor in my life. And I don’t drive like a little old lady, I just avoid braking hard by thinking ahead.


#5

I recently had the rotors put on, after I had the brake system flushed. Pads were changed last year. The feeling in the pedal is not your normal pulsing of ABS brakes. It almost feels like you are running over gravel while pushing the brakes or that you have gravel caught in the brakes somehow. You feel it in the pedal though…like it is jumping under your foot. It does not happen all the time and sometime goes away for several days. Then sometimes…does it several times in one day. It seems like it is something binding or catching or not operating correctly all the time. You always have brakes but it makes you a little nervous when the brake pedal is acting up. It almost feels like a resistance in the pedal…like something is pushing back against the pedal when it does this.


#6

It is also not the same feeling as a warped rotor. It is more like a resistance in the pedal when it does this. The pedal does not go down smooth…it is like you have something trying to pump or not pump correctly. It can be an unsteady pumping sensation sometimes and then other times it is steady but still feels like you have something caught in the between the pad and rotor causing resistance.


#7

Clearly the ABS. I’m going to guess that you have a wheel speed sensor malfunctioning by occasionally not sending a signal and the system thinks a wheel has locked up.