rebuilt brake booster doesnt work

[Cptn. Calzone]

Brake booster rebuilt by top VW brake outfit..all lines master wheel cyls and calipers new or rebuilt(71 Bus) Working with a vacume pump with pressure switch(didnt want to tap my then NEW Raby bus motor intake! Sooo a booster pump which functioned flawlessly for yesrs and in fact fine and dandy with the org booster..which did in fact work quite well...Prev. maint brain said" its 50 years old you did RVERYTHING ELSE Sooo off she went(booster) and came back 3 weeks later all shiny and ready to go....NOT!! Cannot get any boost and straong vacule at the line into the pump new ck valve..what am I doing wrong??
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[airschooled]

Come back with numbers. If you're seeing 18+ inches Hg, and getting no boost, something is wrong. But with aftermarket parts, you are the one responsible for confirming compatibility with measurements.

That, or your check valve is backwards. Arrow towards pump.

Robbie
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[SGKent]

[Cptn. Calzone]

Yes Spoke with the rebuilder the booster is an ATE stock to the vehicle. I will test if I have 18 Hg and the rebuilder suggested I disconnect the booster and drive it to see if there is any change in the braking. I do have good brakes..however I want my booster!! How would I test for a vacume number?
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[aeromech]

Boosters are simple devices. If you got it from a reliable source it’s probably good. Have you replaced your vacuum hoses using gates power brake vacuum hose 27231? 15/32 internal diameter
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[airschooled]

It's more likely there's a hose disconnected, or some masking tape left blocking off the booster port… That's why we measure: 50% to get the results, and the other 50% to get our eyes on the simple solutions we overlook when working tired/hungry/frustrated.

Every chain auto parts store will rent a vacuum gauge. They look like this gallery picture I just found:

To the left, is vacuum, negative pressure, measured in inches of mercury (Hg.) On the right is low-pressure fuel pump testing, for carburetors and feeder pumps up to 10psi. You need to plumb this gauge into the vacuum line from vacuum source (vacuum pump in your case, engine usually,) to the servo. A stock bus will produce between 10 and 18 "Hg at idle, so it's best to be on the higher side so you get multiple pedals presses before depleting the system.

*A good booster/check valve will give you at least 3-4 pushes of the pedal after shutting down the engine. Any aftermarket system should be able to match that, at least.

Most auto parts stores will also have something like this, a universal T. You can chop it to the exact sizes if you like, but leaving it assembled works too, but just takes longer for the guage to respond.

https://www.autozone.com/fittings-and-hose-line-co...373175_0_0

I'd also like to know your vacuum pump make/model once you get this sorted. I'm always on the hunt for a quiet one; every pump I've heard is a bummer.

Good luck,
Robbie
_________________
Elon and Trump messy gay breakup happy pride month 🏳️‍🌈🏳️‍⚧️

One-on-one tech help for your vintage Volkswagen:

www.airschooled.com

https://www.patreon.com/airschooled

[Cptn. Calzone]

This one isnt quiet!! I thought about replacing the entire pump assy as well(its 13 years old may be tired. So new hoses and ck valve tommorrow t in line and then gauge
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[W1K1]

[aeromech]

I’ve only installed one vacuum pump in a bus. It was a bad idea. I did however use rubber isolators to dampen the noise. You can easily find them on amazon
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[OB Bus]

[SGKent]

[Wasted youth]

When you reinstalled the booster, did you properly set the pushrod adjustment?

It’s been several years since I did this, and my memory may be playing tricks on me, but I know when I replaced the vacuum booster on my Vanagon, a small adjustment on the rod makes a huge difference in functionality.

[Cptn. Calzone]

I set the rod where it was and possibly could adjust again(more push) and see ho w that works
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[lil-jinx]

is the vacuum pump cutting out as it should when it reachs it set vacuum or does it just keep running ,and not reach the switch shut off vacuum .if it keeps running I would suspect a leak,or a failing pump ,if it shut off then I would suspect a rod adjustment or a faulty booster ,you may need to adjust the rod at the front as well as at the MC .
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https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy sold dec 2024

1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes.

[Cptn. Calzone]

The pump runs and runs..so I purchased a new switch..NOT the exact switch...It still runs on forever....soooo I am installing ALL NEW vacume lines ck valve and pump...
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[Cptn. Calzone]

I agree the pump may be tired..soo a new on is going in!!
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71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse

[SGKent]

the Bentley explains how to adjust the brake servo rod for 1971 and later.
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[lil-jinx]

if you block the intake for the pump ,can you feel suction ,and will the pump then shut off,if yes to both then the pump and switch is working ,although it don,t prove the switch setting,
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https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy sold dec 2024

1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes.

[W1K1]

[Cptn. Calzone]

Jinkx the vacume is present although not very strong feeling(finger tip gaugelol) and the pump does not shut off..henceforth the whole new pump assy and swithch being installed
_________________
71 westfalia
67 912 Porsche Quintilla
67 Single Cab aka my work horse