this van was left outside for 2 yrs. and the power front disk brakes are just not working well. the calipers seem free, but it acts like it is not getting the assist. vacuum? what item in the power assist may freeze up over time in a rather damp climate?
Have you *actually* moved the caliper pistons inward to see if they are free? They are the most likely item to freeze up.
Disconnect the vacuum line (plug it) and see if there is *less* braking.
Speedy Jim
well, Jim/ I moved the pads outward by opening the bleeder and prying on the pads. fluid came out. there must be a vacuum leak, but I can't seem to find it. hint/ the idle has not be consistent. btw, thanks for all the help in the past. \g
See what blocking off the vac line to servo does. If there is a change in idle, that would say leak. Also, see what it does to braking. The servo's *do* go bad once in a while.
Jim
Well, there does seem to be a change in the idle. but where is the leak? is there a diaphram inside the servo, that could leak? I have a Clymer Handbook on the transporters 71-72 they suggest replacing the damping ring,filter,seal,boot. Have you ever taken apart one of these units? and who has these parts? I've had a few of vacuum assist front disc brake vans, never had trouble. they sure do come to a stop. I have a '77 that I was thinking of scrapping. It has a good servo.
Yes, there is a diaphragm inside. The various seals could be a problem too. A few parts here:
Jim
A Veteran for Peace wrote in news: snipped-for-privacy@sn-ip.vsrv-sjc.supernews.net:
The '77 probably has a much larger servo. There is a check valve on the vacuum line - later models have it inside the engine compartment but I've no experience with '71. There is also (on later models - not sure about the '71) a device they call a proportioning valve. It is mounted at about the center (fore/aft) of the bus, just inside the frame rail. It is intended to limit nosedive and prevent skidding from weight transfer... Follow your brake lines from the MC and look for this device a couple inches across... It has brake lines going in and coming out. It consists of a chamber that the fluid passes through - with a heavy ball that covers an outlet port when there is enough inertia to cause it to roll forward. Those are supposedly non repairable and about $600 (still available from VW a couple years back!) If you remove it to clean it, first get yourself some very thin gasket material as you will need to make your own gasket when you reassemble it. Open it up in a tray so you don't lose any pieces. Clean it and polish it, wash with denatured alcohol, reassemble and flush the entire system with fresh fluid. Those things get all gummed up inside and rusty, too.
Let me know if the '77 servo will fit on the '71 - I have a similar project coming soon!
The servos are supposed to have a filtered vent on the forward side of the diaphragm. The later ones have a hose that picks up air from inside the double wall body area behind the front wheel arch. Mine had gotten a screw driven through the hose by the people who did the camper conversion when it was new. That hole was directly in the spray of the front tire. I knew nothing about it until one sub-freezing morning my brakes were literally frozen. I pushed harder on the pedal until there was an "explosion" sound and no more resistance whatsoever! The servo chamber had filled with water and the water froze the bottom part of the diaphragm in place causing it to break when I got too over zealous with the brake! Expensive lesson learned.
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