brake booster problems 71 vw bus

aeromech · Posted: Mon Jul 16, 2012 1:42 pm Post subject:

I always start with the right rear, left rear, right front, left front but I have a question....

The bay window buses all use a dual circuit master cylinder, right? You have one lower reservoir that pops into the top of the mc but isn't it divided into two compartments? You have a front circuit and a rear, right? So, let's say you work on the right front wheel cylinder. Is there any reason at all to bleed the rears??? I'm just asking.
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busdaddy · Posted: Mon Jul 16, 2012 1:52 pm Post subject:

aeromech · Posted: Mon Jul 16, 2012 3:09 pm Post subject:

That's what I thought. I just did a brake bleed on a 1968 bus and when I got to the right front I found that the hose had a blockage. Bought and installed a new hose so I just rebled the fronts only.
_________________
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

Cptn. Calzone · Posted: Mon Jul 16, 2012 4:01 pm Post subject: Door panels

My window mech gave up the ghost resulting in a dead window down in the door.So I salvaged the proper parts from my bus stash and got ambitious and made some nice wood panels to replace the mush cardboard.I also moved the speakers up ,and in the process I am installing the later bay arm rests as the 71 did not have them.I will attach the marine varnished panels with stainless screws and washer.Pics coming soon!
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Wildthings · Samba Member Joined: March 13, 2005 Posts: 50348

Personally I don't think it matters beans whether you do the front or rear first on a bus with a dual master cylinder and as for right or left it probably matter more to which side the body is leaning than what the manual says. On some machines it matters quite a bit which slave gets bled first but on a dual master cylinder bus not so much at all.

Davidcu

Well, I finally got brake pressure when I adjusted the rear brakes of my 76 Westy. Everything replaced including the brake MC and Servo. Noe my bus dies when I apply the brakes and come to a stop. Do I have a vaccume leak in the brake Servo line?

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50348

Davidcu · Posted: Sat Jul 28, 2012 8:26 pm Post subject:

Well, the servo has been rebuilt and the bus idles low so I will try to adjust the idle and see how that effects the dieing problem. Yes, I do get several softer pumps and then hard pedal when the engine is off.

Davidcu · Posted: Mon Jul 30, 2012 9:42 am Post subject:

replaced the Brake Servo Check Valve and the problem with the engine dying stopped.

Davidcu · Posted: Mon Jul 30, 2012 9:42 am Post subject:

replaced the Brake Servo Check Valve and the problem with the engine dying stopped. Very Happy

busdaddy · Posted: Mon Jul 30, 2012 9:43 am Post subject:

Davidcu · Posted: Mon Jul 30, 2012 9:46 am Post subject:

OK, here is another one. I have replaced the heater fan tht was missing with a used one that works well as I tested it. I plugged in the wiring in the engine compartment to the relay on the ran. When I start the engine and move the red lever on the dash down to whre it makes contact the fan does not go on. Any suggestions. I did check the fuse in the line in the engine compartment and it is good Just don't seem to get any juice when the lever on the dash is engaged. Yes the sire to the lever is connected. Where else would I look? Maye a grounding problem???? Thanks for all your help guys.

Davidcu · Posted: Mon Jul 30, 2012 9:48 am Post subject:

Yes, the arrow on the valve is pointed toward the engine. That is what my Bently's manuel said to do. Is that correct? Rolling Eyes

busdaddy · Posted: Mon Jul 30, 2012 10:05 am Post subject:

Yes, that's correct, odd that it cured the dying issue, maybe it's allowing the booster to store enough vacuum that it smooths out the sudden added air to the engine Confused

I guessed backwards as that would shut off vacuum to the booster and eliminate it from the equasion. Good to hear it's fixed.

As for the fan problem did you rev the engine so the charge light went out? The relay needs a signal from the blue charge light wire to close.
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Davidcu · Posted: Mon Jul 30, 2012 11:38 am Post subject:

No I didn't rev the engine. I will try that. Thanks for info. It's tough to work on these classics because no one seems to know locally and most of them don't care. Oh well. Their Loss! Wink

yachtybugger · Posted: Tue Jan 22, 2013 1:18 pm Post subject:

Just dragging this one up as I have a relevant question, and you guys on this thread appear to know your servo stuff Wink

I've just started a resto on my 71 westy and just removed the servo only to find it full of brake fluid Shocked

I guess I have a leaky master cylinder.

The bus was running, driving and stopping fine and all vacuum lines were connected but now I'm not sure if the servo was working correctly.

I'm guessing its U/S but thought I'd check with you guys before forking out for a new one. Do you think it can be cleaned out or is it now kaput?

busdaddy · Posted: Tue Jan 22, 2013 1:38 pm Post subject:

Cleaning boosters is a roll of the dice, if it's not rusty inside you can try some dish soap/hot water or possibly brake cleaner and dry it out really well and see what happens, if it's full of chunky bits like coffee grounds they will likely end up in one of the valves in there and cause a malfunction.
If it does fail it won't be a life and death situation, either it'll stop assisting and possibly cause a vacuum leak to the engine or it'll start applying the brakes all by itself. Aside from the harder to stop part the bus will still stop.
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Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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CoastalAirCooledVW · Posted: Tue Jan 22, 2013 1:47 pm Post subject:

yachtybugger · Posted: Tue Jan 22, 2013 2:07 pm Post subject:

Thanks guys, I've got plenty of time before I need it again so will try and clean and dry it out. I wasn't sure if there were any rubber seals in there that may have been eaten by the fluid and I would be wasting my time.
When you say rebuilt, what exactly do they do? The Bentley says you can only replace 4 of the outer parts. I took this to mean the actual 'can' bit and the internals are not repairable. Am I wrong?

aeromech · Posted: Tue Jan 22, 2013 2:39 pm Post subject:

From what I understand inside the booster is a spring under fairly heavy pressure and a diaphram. The shops use a tool that allows the can to be split in half so that the internals can be replaced. I've never seen it done though. If you try to do it yourself you could be in for some safety issues.
_________________
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


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brake booster problems 71 vw bus
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