ABS, no pressure

I'm troubleshooting the ABS system (on a Golf III with a 90hp TDI engine) and I'm completely frustrated.
The brake pedal can be depressed with slight resistance.
The master cylinder has already been replaced, so it's not leaking.

Is there possibly a valve in the printing system that isn't closing properly? If so, how can I test this with simple tools, or could the central unit be the problem?

No leaks are visible from the outside.
Brake fluid is new.

Sure, here's the translation:

'Thanks.'
Cyruz.

Is the system really properly bled? Otherwise, I don't know of any other solution.

The workshop installed the main brake cylinder, and then they determined that the ABS compressor is broken, which will cost around €1000 to replace.

It's too much for me to handle, so I want to take charge of it myself.

Could it be that only one valve is permanently open, and all the pressure is escaping through it?

It would be good to know more about the basic functions of an ABS system. Since I don't have any knowledge about it myself, I'll just step away from this discussion. I've never heard of a compressor problem related to ABS before. Otherwise, such a system should be designed in a way that any damage within the system itself doesn't cause a drastic reduction in braking performance.

Hello,

If the pressure pump/compressor of the ABS system is faulty, this should be documented in the ABS system's fault storage (FSP).
What does the FSP say?

Hello.

Before my current car (a "4"), I had a Volkswagen Golf 3 with ABS, manufactured in 1994.

I had a rather large ABS unit installed.
During a brake fluid change, a master mechanic once told me that there are different manufacturers of ABS systems. In my specific version, a relay needs to be bridged or activated in some way during the bleeding process. (That was quite a while ago! My memory isn't what it used to be!!!).
To ensure the ABS compressor runs during bleeding.
Is the relay possibly defective, or did the workshop not consider the relay when bleeding the brakes?

Hi there,
There are some ABS systems that can only be bled with the engine running.
Okay, maybe I should check for air in the system again.

Regards,
Olli.

Before we continue to speculate here, we should first clarify which type of ABS he has.

Is it located under the rear seat or directly on the brake booster? I think it's the "Mark20".

I only know that there are at least these two.

Unfortunately, I can't contribute any more than this – except to say that it's quite risky to tamper with parts of such importance without proper knowledge.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Located beneath the rear seat is, at most, the ABS control unit.
The hydraulic unit is located directly on the main brake cylinder.

It would still be important to know which system it is referring to.

With VAG-COM, it is possible to perform an actuator diagnosis.




Actuator diagnostics.
The actuator diagnosis function allows for testing of the pump motor. Additionally, it can be used to check the correct operation of the hydraulic circuits (the connection of brake pressure lines to the wheel brakes, as well as the functionality of the valves) for any incorrect connections or leaks.

Sure, here is the translation of the text from German to English:

'Note:'

'The vehicle must be lifted so that the wheels can rotate freely. (A second technician is required to turn the wheels).'
You can exit the testing process at any time by pressing the 'C' key.
'After repeated pressing of the brake pedal, the vacuum in the power brake booster is reduced. As a result, more force must be applied to the brake pedal to achieve the same fluid pressure in the braking system as with vacuum assistance.'
'If there is a loss of vacuum in the brake booster, it may happen that the wheels do not lock up. In this case, start the engine to restore the vacuum in the brake booster.'

Oh yeah.
Bleed:


Bleed brake system, vehicles with and without ABS, ABS/EDL.
Vehicles equipped with ABS/EDL.

The 'Basic Adjustment' function is only necessary for vehicles where the brake fluid reservoir has completely emptied (e.g., due to leaks in the braking system). => Refer to the 'Vehicle Dynamics and Diagnostics Manual'; initiate the basic adjustment.

Otherwise, the normal bleeding procedure should be followed.

Thank you, thank you.

I'll check and test everything today or tomorrow.

Let me know when I have gained new insights.
Unfortunately, the car isn't with me; it's at my parents' place.
That's why it all takes a little while.

Sure, here's the translation:

'Thank you.'

Okay, it took a while, but:

You were right. It wasn't properly vented.
And things like that happen in a workshop; you just wouldn't expect it.

Good news then: He's slowing down again.
Bad: The power brake booster is almost not working.
A minimal effect can be observed, but you really have to apply a lot of force for the tires to lock up! By the way, ABS still works.

According to the testing device, the BKV should be functioning perfectly.

Are there any common failure points for this that I should be aware of so I know where to start looking?

Sure, here's the translation:

'Thank you.'

And the vacuum pump?
Do they provide enough vacuum?
Are all the vacuum hoses intact and free of cracks?

Well, shouldn't a defect in the pump be visible through a diagnostic tool?

Okay, I haven't checked for cracks yet, but I think they're difficult to spot.

Well, shouldn't a defect in the pump be visible through a diagnostic device?


I'm not aware that it's possible to diagnose faulty vacuum pumps using a diagnostic tool, especially not with the G3 system.



Cracks in the thick black hose connecting the vacuum pump to the main control valve are usually easy to spot.

Okay, then I'll definitely check that out tomorrow!

'Please translate the following text from German to English. Provide ONLY the translation, no explanations.'