hard brake pedal after many pumps, vacuum issues.

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Had the same issue as you, tried the same fixes with the pump nipple with no luck. Measured vac at the pump outlet and it was low. Pump was worn. Should have been there first thing I checked but hoses, etc were due so I did all that with no changes first.

Take a mighty vac, hook it to your vac pump, report back what happens. It should climb within a few seconds to 25Hg (+/-) if in good shape. Mine was taking 30+ seconds to produce that type of vacuum and hardly reached that number, even with the nipple "fix"

For what they may be worth, here are a few comments on my experiences dealing with vacuum.

I installed a vacuum gauge for the 02 ALH in my Vanagon. Observing the gauge is quite informative. Depending on elevation, the vacuum system hangs around 23 inches.

Pumping the brake pedal will drop vacuum rather fast.

A good tight vacuum system as well as a good pump will maintain a constant level of vacuum that will only show a blip in vacuum reduction when the brakes are applied. Boosting use of vacuum is really not noticeable.

I did the nipple seal with JB Weld years ago and it has held with no vacuum leak or oil mess.

Make sure the vacuum reservoir and hose are functioning properly. There is a check valve that should be examined also.

2.2TDI said:

Probably gonna sound dumb but I'm guessing the vac test on the pump should be done with the car off, or on?

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Car needs to be running since the vac pump is driven off the cam.

Check the vacuum actuator on the turbo and see if it will hold vacuum. Hook straight up to it and pull a vacuum

Sent from my SM-N975U using Tapatalk

Humor me, why are you pumping the brakes while driving? 10 frantic taps? I don’t touch my brakes in any vehicle until I come to a stop sign/ red light and I never pump them, just a slow steady constant pressure on the pedal for a smooth stop. Or in the case of a deer jumping in front of me one hard frantic jab.

Why are you pumping them, are you creating a problem that you may not even have?

A little lesson.

Your brake booster is just a big vacuum chamber with some sort of diaphragm in it. Under normal circumstances, car running, both sides of that diaphragm are under vacuum, provided by your vacuum pump. As soon as you press the pedal, it breaks the seal on that side of the chamber, and lets it atmospheric pressure. The combined pedal push, with atmospheric pressure on one side and a vac being pulled on the other side, makes it easy to apply the brakes. You have assistance. Now, when you apply the brakes 10x in a row in short bursts, the vac pump cannot keep up and supply enough vacuum on the matter cylinder side. Your pedal then goes hard. This will happen on any of our fully functioning systems. If your brakes go hard, they usually do in a few pumps if not less. Depending on the severity.

Also, that little ball in the engine bay? Another vacuuum chamber. That little guy stores up reserve for the rest of the system (turbo) so you have some functionality for a bit if the pump starts failing and can't keep up with the system.

You won't know for sure until you replace the actuator with a good one.

2.2TDI said:

So looks like the actuator doesn't hold vac... There's a cheap used turbo near me that has an actuator, will scoop that up and keep it as back up
Now if the actuator doesn't hold vacuum, what does that mean in terms of the brake system?

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The brakes and the turbo are separate in the vac system. The only thing that links them would be the source, which is the vac pump. The actuator not holding vac would explain the turbo, but not the brake issue.

Hi everyone,

I recently bought my first ALH ('03 Golf) from a private seller that recently had a TON of parts replaced (including vacuum pump, head, clutch, A/C, brakes, suspension, etc. etc. etc.) and I seem to be getting this same exact behavior - after several pumps of the brake pedal, the pedal gets really hard and most, if not all, braking power is lost. However, when I hold the hard brake pedal with a firm left foot, and tap the accelerator pedal with my right foot, the brakes come back almost instantly, the brake pedal depresses again, and I get braking power back.

I noticed this initially when getting off a highway exit when I was "modulating" the brake pedal to come to a perfect stop right at the stop light. After a few "modulations" i.e. pumps, the pedal got really stiff and I lost braking power. Same thing happens when driving through a parking lot, say, when I'm on and off the brakes a lot dodging people and other cars.

I intuitively get how pumping the brakes can "exhaust" the amount of vacuum available for brake assist, and that following this "exhausting" of all the available vacuum, it either takes time for the vacuum pump to build vacuum back up with an idling engine (i.e. coasting down the exit ramp to the stop light), or you can get vacuum back up quickly by revving the engine. But is this seriously normal? I find it difficult to believe that VW engineers would make this sort of braking operation standard on an early 2000's automobile; however, again, this is my first 'older' VW I've ever owned and I could be completely wrong.

Pumping the brakes went out in the 70s ?
Am I missing something?
There is no good reason to pump the brakes, please learn how to drive. Both of you.
Cheers

muzy said:

Pumping the brakes went out in the 70s ?
Am I missing something?
There is no good reason to pump the brakes, please learn how to drive. Both of you.
Cheers

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Gees, what an incredibly helpful response. My first post on TDIClub soliciting simple help from others, and that's what I get. Brilliant.

It's not an issue of "knowing how to drive." I lose significant braking power upon pressing the brake pedal only one extra time after pressing it initially. And it obviously gets worse from there. It's not like we're sitting here pumping the brakes multiple times every time we come to a stop.

I'm just asking if this is normal or standard operation for this car's brakes, or if something else could be wrong.

Thanks for the thoughtful response though.

There's no spec that I know of for this, so all I can comment on is my own experience.

Every VW I've ever driven is good for 4-5 identical pumps of the brake pedal before I sense a noticeable increase in pedal effort. I don't expect to be able to do more than 4-5 'cause I know the engine doesn't produce full vacuum at idle and the reservoir is pretty small and can only compensate for so much.

The times I've had a braking effort increase after 2-3 pumps I've investigated further and found an issue.

If you're experiencing a noticeable difference in braking assist on your second pump I suspect you do have an issue, and you'll probably be able to find some pretty good troubleshooting threads here. Old hoses with cracks, the check valve, and the rubber seal at the master cylinder (as discussed above) are the common suspects.

muzy said:

Pumping the brakes went out in the 70s ?
Am I missing something?
There is no good reason to pump the brakes, please learn how to drive. Both of you.
Cheers

Click to expand...

Yeah. You didn't read all of the posts and came up with a conclusion.

jokila said:

Yeah. You didn't read all of the posts and came up with a conclusion.

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I am sorry Jokila, I read all the posts a couple times, some more then others.
I have never heard of a test for braking system performed in the manner in which they were administering the test.
https://www.tc.gc.ca/media/documents/roadsafety/135_TSD_rev_3.pdf

In the link section S7.11.3 page 33 and other sections deal with expected performance from a light duty vehicle.
How there testing methods were confirming or denying real life expectations
is beyond my grasp.
My post is addressing there concerns, or at least voicing what I thought the issue was. How dose your post address there brake issue?
cheers

Hey all,

Not to resurrect an old issue, but thought I'd update you guys regarding my issue I posted about above.

Simply put, turns out I had a cracking vacuum pump to brake booster pipe. Installed a brand new replacement and not only are my brakes 1000x better, but engine shutdown is A LOT more smoother now.

Turns out my issue wasn't "not knowing how to drive" hahaha

That tube is known to crack.
May not be easy to see w/o removing it.