Brake Booster Issue

[davebuckholts]

[pantone149]

Power Brake Exchange in San Jose, CA. Good price, good work, the same part that came out goes back in.

[jtauxe]

[jtauxe]

New brake booster issue:

In the 1972 Sportsmobile, I had a vacuum leak in the booster line, so I replaced the line. I also had to free up the check valve, and it all seems to hold vacuum, since the engine runs fine hooked up to the hose, which is connected to the booster servo.

Braided 12-mm vacuum hose from Bel-Metric:
https://www.belmetric.com/braided-metric-hose-oem-...p107f12u67
It's nice, but does not have the steel reinforcement coil.

But - still no boosting action. The brakes work, but there is no servo assist.

I figure that this means that the brakes, wheel cylinders, and master cylinder are all working. The bus does stop fine if I really stomp on the brakes. There are no identifiable leaks in the system.

Does this mean that the booster has failed in some way?
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD

[kreemoweet]

It's not clear how you verified that vacuum was actually reaching (and staying in) the booster. Got a vac gauge and a tee?
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[aeromech]

If it was me I'd adapt my mityvac to the vacuum port on the back side of the booster and pump it down. The mityvac has a gauge on it and a person can watch to see if it's leaking.

_________________
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

[jtauxe]

Admittedly I am relying on indirect evidence. If there were a vacuum leak, like there was before I replaced the hose (and had to plug the ports on the dual carbs), then the engine would run like crap or not at all, really. Now with the new vacuum hose installed and connected to the ports on the carbs (well, connected to the splitter tube that penetrates the firewall, actually), the engine is running well. That tells me that the hose is holding vacuum. Since I verified that the check valve is working, does this not imply that I must have vacuum all the way to the booster?

Or is there a flaw in the logic...?
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD

[aeromech]

Did you get the check valve in backwards?
_________________
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

[jtauxe]

[kreemoweet]

[captincanuck]

[TomWesty]

[jtauxe]

[W1K1]

I recently got my 71 westy (EJ2.5) running and driving. When I had it in for the inspection I found the check valve was in backwards as per the bentley, once we swapped that around the brakes have more stopping power.

But from the descriptions of proper working brakes it still seems like they could be better? it's been a long time since we've had a bus.

the brake booster is definitely pulling a vacuum, the idle goes up when you press the pedal, you can hear the booster pulling air into it and the idle goes back down. The pedal is firm when you are braking.
everything is new or rebuilt except the booster, it came with the bus, and he said it was a known good booster, the one on the bus was crusty rusty

How much vacuum should it be holding?
how much added stopping power should you get from the booster?
_________________
http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[SGKent]

to test the vacuum.

Start the bus with the parking brake on and your feet off the brake. Let it idle a minute. Turn the engine off. Do not step on the brakes yet. Wait 5 minutes and step on the brakes. The first step should feel normal, the second time you step on it, it will feel normal, the 3rd time it will get hard to push because the vacuum has been used up. If it is hard from the beginning and does not change then your booster, line or check valve is leaking. The check valve holds the vacuum in the booster.

Test 2. With the vacuum used up in the test above, hold the brake down and start the engine. You should feel the brake pedal move down a little more when the vacuum from the engine hits it.

It helps a little to have the hand brake off during these tests but you will have to chock the wheels if you do this. I usually have the hand brake on. I do these tests every few months just to be sure the booster is working right. You can almost do it by habit - meaning you stop the car, put the emergency brake on, turn the engine off and after 20 -30 seconds step on the brakes a couple times. You'll feel them get hard as the vacuum gets used up. FWIW my bus sat in a field for about six months before I bought it. The booster still had vacuum in it. They are not supposed to leak at all, but if they can hold vacuum for 5 - 15 minutes then you will be good to go. If the vacuum is gone in a minute or two then something is leaking - e.g. booster, line or checkvalve.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[kreemoweet]

Engine speeding up when brake is pressed means the booster valves are leaking. It is when you let UP on the pedal that a little bit of air gets sucked into the engine, and it is not really enough to speed up the engine. I have to pump the pedal like a madman to have any effect on engine speed. The booster should hold 100% of whatever the vacuum in the intake manifold is.
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[aeromech]

Booster out and sitting on my toolbox. Made a rubber plug for where the master cylinder goes. Used my mityvac hooked up to the vacuum port. Had to pump about 100 times but finally pulled a vacuum of about 15 inches of hg. It held for 15 minutes so I’m calling that a good booster
_________________
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

[W1K1]

[W1K1]

Okay , now I see how it should stop

I bought the Wolfsburg west booster, installed it last night and it stops like a new car.
_________________
http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[Shonandb]

Good to hear that you got it sorted.
_________________
*******************************
76 Westy with a 2.5L Subaru SOHC + Vanagon (010) Automatic Transaxle
Build & Trip Thread: https://www.thesamba.com/vw/forum/viewtopic.php?t=758760
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