Vacuum Leak: How to Find and Fix It

Hey everyone,

I've noticed that the brakes on my Passat (3BG, 74kW, PD, manufactured in 2001) lose pressure after the car has been parked for several hours.
When I turn off the car, the brake pedal still has the power of the brake booster (so you have to pump it a few times until the pedal "hardens"). However, if I get into the car the next morning, for example, the pedal is hard from the beginning.
I've only ever experienced it where the pedal remains "soft" for weeks.
At the very least, I suspect I have a small leak in the vacuum system.
Right from the moment you start the engine, the pedal becomes soft again and remains that way during the drive, as it should.

How should I proceed with troubleshooting? I've already checked the hoses, but everything looked fine to me...
Is it possible to use a jump starter there, or would that help?

Or am I completely wrong in my assumption that there's a leak?

Best regards,
bad_taste

If it makes you feel better, my Passat does that sometimes too.

When searching for vacuum leaks, you encounter the problem that a "search medium" is sucked in. It disappears as a minimal amount. In contrast, when searching for pressure leaks, it bubbles out, towards you.

There are many potential candidates to consider, especially when you think about all the places where vacuum is used.
- Braking force
- VTG from the turbo.
- Shut-off valve
- Exhaust gas recirculation (EGR)
- If necessary, cool the EGR system.

Starting fluid doesn't do anything because it's so volatile that it evaporates before you can even tell if it's working.

m;

The only thing left to do is check the hoses. A classic place to look is the hose from the tandem pump to the main pressure valve, somewhere near the check valve. That's where mine was torn.

Could you clearly see the crack? Did you remove the hose for inspection?

(And where on earth is the tandem pump, and who is the BKV?)

It looks like I need to take out all the hoses one by one and check them individually. It's not a problem, since I have about 5 elbow joints per arm and roughly two to three small hands per arm...

"Is it possible to buy these connector pieces, i.e., this fabric-covered hose, as a roll of material somewhere? Or is this some kind of special hose that you can only buy in 5-cm pieces for 5 euros each from a specific supplier?"

1. Clear visibility - often requiring modifications or extensions.
2. The brake force amplifier is located near the black hose, which leads to the tandem pump on the side without the timing belt, behind the camshaft (ha, ha), towards the transmission.
3. Only use original parts - do not modify! Risk of serious injury! Risk of liability...

There are always those impatient people who ask the same question in multiple forums .

Bye.
peace

pax wrote:

There are always those impatient people who ask the same question in multiple forums at once . Bye. pax

With the diesel mechanic, you tend to get answers more quickly.

Hi,

Please stick to the topic. The posts in various forums are more for comprehensive troubleshooting than for providing a "quick answer."

If I have time this weekend, I will thoroughly check all the hoses, especially those on the brake booster. (Since I'm not lazy about writing and I'm not a fan of abbreviations, it sometimes takes me a little longer to understand things ).

If anyone has a great idea, please don't hesitate to share it. Also, I will let you know if I find a suitable position.

Best regards,
bad_taste

No, you can't see the crack just by looking, because no oil is leaking out. A mirror won't help either. I would start by checking the tandem pump and then search towards the main control unit (BKV), and then in the direction of the vacuum reservoir (a black plastic ball, about the size of a tennis ball). It's best to remove the plastic cover above the engine, as this will give you very good access to the vacuum lines, which are located quite high up. By "very good," I mean better than in other cars .