Brake Pedal Problems: Squeak or Spongy Feel?

Hello everyone,

Once again, my Leon ARL is exhibiting some strange behavior.
This time, thankfully, it wasn't the engine, but the brakes, which weren't particularly good to begin with.
The description of the problem is a bit difficult to understand, but I can say that I've ruled out air in the system and old brake fluid.

When pressing the brake pedal while the car is stationary, both with the engine running (vacuum supply to the brake booster) and without assistance, the pedal makes a brief clicking sound approximately two-thirds of the way down. From that point, the pedal can be pressed very easily and with significant travel.

When you slightly release the pedal, it gives the impression that there is 'play' or slack in the system.
The pedal feels very spongy.
However, this only lasts until you reach the point where the 'cracking' sound returns.


Is there a connection to ESP (Electronic Stability Program)? Is it related to the brake assist system? Or is it perhaps a normal occurrence?
Are there any comparable vehicles that also have this feature?

To be upfront: I am absolutely not an expert when it comes to brakes, but rather a technically interested driver with a general interest in the subject.

In the vehicles I've driven so far, I've noticed a "stiffness" or "resistance" in the brake pedal, where it becomes easier after a certain point, but I've never encountered anything like it before. Therefore, I suspect there might be an abnormality with your brakes.

Two questions:
1) You write that this occurs both with and without the engine running. However, does it also happen without ignition (i.e., without electrical assistance)?
2) Does it still occur when the vacuum is depleted by repeatedly pumping the brake pedal without the engine running?

If it happens in both cases, I suspect the master cylinder. However, I'm just a layman when it comes to brakes.

Regards,
Sure, here's the translation:

"Guste" is a German word that means "gust" or "gust of wind." It can also be used to describe a sudden burst of something, such as laughter or anger.

It occurs in both cases, and also while driving, regardless of the speed.

Are there any Leon drivers who might be able to check this on their own car?
Maybe it's even normal?

"I'm familiar with this from the G IV with ESP. This is how the mechanical BAS feels. When it activates, you can press the pedal further without any additional resistance until you encounter a very strong resistance. At that point, full support is suddenly engaged, meaning you are completely held in the harness."

The trigger can be activated by either very quick pedaling with moderate force, or by pedaling very forcefully.

Yes, that might work, but the mechanical aspect is always the same.

The speed at which I pedal hasn't shown any differences.
ESP is definitely something the lion has, but was BAS available with the MK20?
I'm not sure about that. Generally, I would assume yes, because they are likely to have a similar design, like the G IV.

It's still unclear whether this is normal or if the HBZ (presumably a piece of equipment) is malfunctioning.
'Does it crack' in the G4 position?

g1om wrote:

a but was there BAS with the MK20?

Yes.

Quote:

"Does it crack" in the G IV?

Yes.

//edit:

BAS G IV Examination Instructions:

Quote:

Press the brake pedal with the engine running to ensure full vacuum assist. When the brake pedal is fully depressed, a "click" should be heard, indicating that the mechanical brake assist system has been activated. Upon releasing the brake pedal, a significantly reduced amount of foot force is noticeable.

@g1om

Your TS or FR model has an HBA (hydraulic brake assist), but your description doesn't apply to other Leon models, and it's not normal. I suspect there's a defect in the master cylinder.

Thank you, I wasn't aware of that instruction regarding the exam.

In this case, I would consider this to be normal and wouldn't exchange anything.
Maybe I'll find another antique at my friend's place in the parking lot where I can try it out.

Thank you for your help.