Brake Booster Issue

[orwell84]

Just adding my own experience to this thread. Brakes were feeling a bit weak especially when coming to a complete stop, along with an increase in idle speed when brakes were applied. Went through all the vacuum hoses and connections to rule out a simple leak. But fairly clear it was the booster.

Brazil booster was the best I could find at the time. I was aware of the fitment issues from this thread. The studs are in a different place compared to the original. It’s not just a matter of drilling new holes. The original bracket is too narrow. I bought a strip of 1/2x1/8 steel from the hardware store because I was too lazy to cut metal and welded them on to the original bracket. Made a pizza box template with old/new holes and drilled new holes. Took me more time than expected but it’s a solid repair.

I had a used booster I got from the classifieds but it was too mauled for a rebuild.

Sometimes you get lucky with the classifieds. Sometimes you get burned. Was advertised as booster from working bus. Word of advice when parting out buses: Pull parts before it goes to the crusher, not after. And don’t use a splitting maul to remove parts.

My original booster looks like a good candidate for a refurb. It’s all there, just leaky.

The Brazilian booster works great. Stops on a dime with no pedal effort. This is the way servo assisted bus brakes should feel. If you have been driving for a long time with a leaky booster like I have, your first stop at speed might feel like you’re gonna get thrown through the windshield.

[poundman]

[aeromech]

I think you’re missing my point. Go back to your preferences and fill out your location and year of your bus. Then, when you post people will know that info and can better help you.
_________________
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

[poundman]

[aeromech]

The front side is just a vent to atmosphere. The rear goes to your engine. What year bus do you have? You might add that to your signature line along with other info maybe, like location
_________________
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

[poundman]

I removed my MC and disconnected the pedal linkage. My MC and booster are definitely corroded. The booster was full of brake fluid. I have another question. Where does the vacuum line from the back side of the booster attach? And where does the air hose from the front side attach? thanks
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Restoring a 1972 Bay Window Bus that has not be registered for the road since 1981.
Sugar Land, Texas

[aeromech]

In all my years I’ve never seen a frozen brake pedal mechanism and I think other than a visual inspection and a quick squirt with some spray lubricant, you’d be wasting your time disassembling your pedal.

If you want, you could remove the long rod from the booster to the pedal and then try your brake but it’s even easier than that. One end of that rod has a fork and a pin. Remove the cotter key, remove the pin, then pull down on the rod and it will disconnect to your pedal. At that point you’ve separated the system in half.

The rod is 25A in the illustration
_________________
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

[poundman]

Thanks, I suspect the MC is the issue but I will remove and test the pedal. I think I will have them both rebuilt. I have sent email to Karps. Any other suggestion for rebuild. I am in Houston area but don't mind shipping.
_________________
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Restoring a 1972 Bay Window Bus that has not be registered for the road since 1981.
Sugar Land, Texas

[aeromech]

If a visual inspection fails to find a cause I would probably remove the master cylinder. Press on the pedal. See what happens. In my mind, the brake system is going to need a full rebuild anyhow, so bleeding is going to be necessary anyway at the least. I’m thinking that you have rust inside the mc causing your jammed pedal. Water gets into the brake fluid and after a long time would freeze the spool in the mc
_________________
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]

[poundman]

Question. I have issue with my recently purchased 1972 bus that has been setting for over 20 years in storage. Engine not running yet but the brake pedal is hard as a rock and will not budge when I try to press. How can I troubleshoot the issue with no working engine. I am not sure if the problem is with MC or the booster. PO said it needs a new MC but I am not sure if that is the case.

What is the latest opinion on replacement vs restore?

Thanks.
_________________
-----------------------------------------
Restoring a 1972 Bay Window Bus that has not be registered for the road since 1981.
Sugar Land, Texas

[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
Previous 1973 Panel Bus:
Click to view image

[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

[W1K1]

[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

[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.
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'67 bug: seized by the authorities
'68 bug: seized by the authorities
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[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

[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

[jtauxe]

[TomWesty]