Jerky braking

Hello,

I drive a 1997 Passat 3B. Last week, I had the steering rack and the upper control arms replaced at a BOSCH service center.

Since I got the car back, I've noticed a slight jerking sensation while braking fairly often. The brakes are therefore not working evenly.

When driving at a slow speed and lightly pressing the brake pedal (allowing the brake pads to lightly scrape), an intermittent scraping noise can be heard from the front left wheel well, not a continuous noise.


The thicknesses of the brake pads and brake discs are still well above the wear limit.


1. What could it be, or what might be causing this stuttering/jerking?

2. Could the workshop (accidentally) have caused this?

Hi,

verdiener wrote:

1. What could it be, or what might be causing this stuttering/jerking?

Based on the entire error description, it sounds like the brake discs are warped.

Quote:

2. Could the workshop (accidentally) have caused this?

Only if someone had hit the brake disc extremely forcefully with a hammer, or had subjected the disc to similar forms of abuse. Therefore, I'm inclined to say no.

That certainly sounds like warped brake rotors.

If the workshop performed a test drive similar to what Michael Schumacher might do after completing the work, it's possible that they tightened the windshield wipers a bit too much. It shouldn't happen in a good workshop, but I've seen mechanics who live out the 'Schumi complex' with customer vehicles...

Regards,
Private.

...or messed around with the brake discs, leaving black greasy fingerprints, and then skipped using brake cleaner.
While it's not as noticeable as warped glass, it's definitely something you can observe.
My second-to-last premium workshop was very stingy when it came to replacing brake discs. Once wiped down with brake cleaner, everything was perfect.

Best regards, Rainer.

Based on the symptoms, I also thought it might be warped brake discs. But I didn't know that something like that could happen so suddenly, for example, due to a sporty riding style.

Will it get worse over time?
It can't be the brake pads or calipers, right?

Hello!

Has the vehicle been sitting in a humid environment or in the rain for a day or two? This slight shuddering can also occur when rust has formed on the areas of the brake discs where the brake pads make contact. These short-lived rust patches also cause the shuddering, but they will wear away over time. Based on my experience, I often don't need my car for a whole week.

Greetings to you all.

Peter.

Hi,

Since the brake discs are no longer fixed to the hub by screws, they are now only held in place by the wheel bolts.
Especially during wheel changes, dirt can easily get between the contact surface of the wheel hub and the brake disc. Following this, there's a slight wobble, which manifests as a subtle, rhythmic grinding at low speeds and as a rattling sound at higher speeds.
If the workshop has removed the wheels...
The inspection can be performed using short wheel bolts and a dial gauge.

Olli.

Regarding the issue of brake shudder, here are my experiences:

1. The discs often make a grinding noise shortly before reaching the minimum thickness (especially under heavy load).

"Our Polo 86C had severe grinding noises due to seized brake pads (resulting from prolonged parking after a winter drive with a lot of salt). After replacing the brake discs and pads (which were due for replacement anyway), the grinding noise only subsided for about 500 km, after which it became even stronger, similar to a pulsating ABS. My own measurement with a dial gauge revealed a thickness variation of approximately 1/10 mm around the circumference of one disc. I was unable to measure the lateral runout. The right wheel showed a noticeable blockage at one point when manually rotating it. Only a second replacement, this time switching from Brembo to ATE brake discs, brought a lasting improvement." Now, it has traveled approximately 5,000 km with the quiet brakes, and the spare parts dealer was able to issue a credit.

3. The rattling sound could very well be caused by dirty windows, as previously reported. A careless workshop can cause other problems as well. For example, the car should not be pushed with the drive shafts removed, as this will overload the wheel bearings. However, I don't yet have experience to know if a defective wheel bearing will ultimately manifest as a rattling sound similar to brake noise. If, for example, a brake disc falls off during disassembly, it can also get damaged.

Hi,

I once had problems with rubbing because a piece of rust was stuck between the disc and the wheel hub. Since then, I generally use a powerful drill plus a wire brush to address the issue -> no problem at all . You can also see such irregularities by carefully examining the mating surfaces. The same applies to the mounting surface for the brake disc .

sorry, I overlooked Olli

Hello!

I heard that there's a shaking or vibration when braking (and the higher the speed, the more pronounced it is).
the harder you brake, the more it jolts) and also from defects (I'm not sure about that anymore).
(certainly) ball joints (?) and control arms (?).

Best regards.
Peter.

If your steering linkage is worn, your car may start to swerve when braking hard (This reminds me of something ). But there shouldn't be any stuttering or jerking.