Brake Booster in 71 bus needs rebuild AGAIN?

Harveybacon

For now, got my brake booster (servo) back on and painted the ol bus. Brake booster was working great, and now is whining and seems to be busted again. I'll have to mail it back out for another 3 weeks to hope they fix it. Would there be something causing it to break? push rod, or vacuum line? everything seems to be wrong in the booster; I think lines are in good shape...
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SGKent · Posted: Thu May 19, 2011 8:21 pm Post subject:

are you leaking brake fluid into it?
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Harveybacon · Posted: Thu May 19, 2011 8:43 pm Post subject:

maximan1 · Posted: Fri May 20, 2011 8:48 am Post subject:

You replaced the brake booster without replacing the master cylinder? I was under the impression that those went hand in hand, usually a brake booster goes out when the MC leaks brake fluid into it.
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Harveybacon · Posted: Fri May 20, 2011 8:57 am Post subject:

ccpalmer · Posted: Fri May 20, 2011 9:40 am Post subject:

Harveybacon · Posted: Fri May 20, 2011 9:47 am Post subject:

thanks, I just bought the bus for 900 and got 230 in credit to the place MAMW. so it's technically free, and I'm not skimping in theory, lol. Is there a way to check if there is a leak? I didn't notice any fluids when I replaced the part. The guys up at the import shop that sent out booster for me feel that the rebuild people could have just made error and there is no charge to send it back. I just need to know what to do to check the situation out. Thanks for the input guys!
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1971 Campmobile
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ccpalmer · Posted: Fri May 20, 2011 9:51 am Post subject:

Harveybacon · Posted: Fri May 20, 2011 9:52 am Post subject:

also, I need to know if it is going to harm anything to drive it like this. The brakes feel way better since rebuild. But started whining, and revving up when braking. It's not too hot here in FL right now, but would traveling like this hurt any other components? I mean it only revs up when stopping, so of course I'm not using the gas then anyways... Anything going to get worn out that I'm not thinking of? Thanks
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1971 Campmobile
M-Plate: http://www.vw-mplate.com/mplate-6571.htm

ccpalmer · Posted: Fri May 20, 2011 9:55 am Post subject:

Harveybacon · Posted: Fri May 20, 2011 10:04 am Post subject:

Harveybacon · Posted: Fri May 20, 2011 10:27 am Post subject:

so pulled hose off carb, stuck a perfect stick in hose, and tightened clamp, threw it to the side of compartment. And I found perfect rubber stopper and put it on carb post/hole. Brakes are hard, but work, and there is no Revving! good thinking. just like before I had it rebuilt, but without revving. Hopefully this is OKAY!?

If I left the hose unplugged (no stick) would that be okay? still curious how vacuum works on this, would it being open hurt anything? Thanks!!
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1971 Campmobile
M-Plate: http://www.vw-mplate.com/mplate-6571.htm

aeromech · Posted: Fri May 20, 2011 10:34 am Post subject:

If I left the hose unplugged (no stick) would that be okay? still curious how vacuum works on this, would it being open hurt anything? Thanks!!

You can leave the hose open. When you pulled the booster did you replace all the vacuum hose? There are two pieces, one in front by the booster and one in back that you plugged. Replacement hose is widely available. Use Gates 27231 power brake booter hose. It's 15/32 inside diameter.

What about the check valve? Do you have one? Is it pointed the right way?
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Harveybacon · Posted: Fri May 20, 2011 11:02 am Post subject:

aeromech · Posted: Fri May 20, 2011 11:09 am Post subject:

I can't seem to find any check valve, unless inside booster. I have read about them, but have no evidence that there is one on my 71 bus.

This is bad. You need a check valve. Also, you spoke about a small hose being in good shape. Which is that? These hoses can fail internally and look good on the outside.
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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

busdaddy · Posted: Fri May 20, 2011 11:09 am Post subject:

The check valve is in the line between the firewall and the manifold (should be anyways).
I'm not so sure you can blame the master for the failure unless it's obviously leaking fluid, same with pushrod length and vacuum plumbing. If the end of the master is dry the only reason for a failure this soon is a bad rebuild (it happens to the best of shops sometimes).
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Harveybacon · Posted: Tue May 24, 2011 6:01 am Post subject:

WELL, i CAN REPLACE THE HOSES THAT HAVEN'T BEEN, JUST FOR PRECAUTION. i SEE NO CHECK VALVE INSIDE ENGINE COMPARTMENT.

Is it okay to drive without power, as I have it now? I don't want to mess anything up doing it this way either. Thanks
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Facebook: http://www.facebook.com/groups/GainesvilleVDubClub
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1971 Campmobile
M-Plate: http://www.vw-mplate.com/mplate-6571.htm

aeromech · Posted: Tue May 24, 2011 6:08 am Post subject:

Desertbusman · Posted: Tue May 24, 2011 8:40 pm Post subject:

gd420mj · Samba Member Joined: March 19, 2002 Posts: 22 Location: NJ

Since this thread is about rebuilt brake boosters... quick question.

I had mine rebuilt a few years ago by that guy in texas...I have not driven the bus much in those few years. Been garaged. However, even since last year, brakes are not quite right....

My question is this: When I depress the brake pedal, even just 1/2", the servo seems to suck air from the front vent on the push rod. I just pulled off the hose and was blowing into it. I pulled the brake pedal down and the servo immediately leaks air. Even if suck, pull vacuum, it still pull air.
IS THIS RIGHT? the engine revs then stalls out, sometimes it doesn't stall..But there is a vac leak.

So is this booster shot again, after only a few years and less then 5k miles?

I am replacing the MC right now so I will check for leaks. Check valve is in place and no gasoline in vacuum lines. (another cause if servo failure.)

SUcks, as I am driving to VA from NJ in morning to finally get in some much needed camping..

74 westy


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Brake Booster in 71 bus needs rebuild AGAIN?
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