German Chocolate heads for the hills

[rustybutterknife]

[Wasted youth]

UPDATE:

1) I disconnected the vacuum line at the top of the servo unit, and tested the vacuum on the line from there. I noted it will build up a decent vacuum using my hand held vacuum pump, but it leaks down from about 10 PSID to zero in about 10-12 seconds, so there is a small leak in the line.

2) I then tested the vacuum on the servo unit itself, and it builds up vacuum and holds it nicely, until the brakes are applied, then goes to zero.

3) With the brakes fully applied, I re-checked the vacuum on the servo unit and again I can build vacuum and it holds, until the brakes are released.

4) I decided to see if there was any air in the brake lines, and started bleeding them...right front, then left front, and checked my progress. Didn't bother with the rear brakes at this point. Brake fluid was being consumed in the bleed jar, but no air was coming out of the system. I noticed a gurgling, splashing sound coming from the booster when my assistant depressed the brake pedal, which I assume indicates the fluid is passing through from the front of the master cylinder into the servo unit. The small weep hole at the bottom, 6 o'clock position on the master cylinder has moisture and bubbled when the assistant pressed the brakes.

I reconnected the vacuum line, and started the engine and applied the brakes. There was a noticeable improvement in braking, but there was too much travel in the pedal. Pumping up the brakes improved the braking effort, but caused the engine to nearly stall, confirming a vacuum leak.

With the engine warmed up and the vacuum port plugged I checked idle RPM, then with the line reattached, I noted about 100 RPM difference in idle speed.

NEXT: Find vacuum leak and repair.

I think the master cylinder is passing fluid forward into the servo unit. I would like to confirm this, and reading the Bentley I am understanding that the master cylinder needs to be removed before the servo unit can come off.

To test the MC, I need to remove both the servo and the MC, then reinstall the MC to see if it is leaking under pressure, correct?

Also, I have rebuilt master cylinders before, and am not interested in getting some aftermarket crap, but I have not rebuilt one of these. Any thoughts on this would be appreciated.

[Desertbusman]

Leave the booster on and remove the MC. If there is brake fluid in the booster the MC is shot.

I don't really understand how you are using you hand held vac pump. Unless you are using it from the hose connection at the engine then the check valve is fighting your test. FOrget about the hand pump and just use the vacuum from the running engine.


Also, have you pulled off the check valve and cleaned and inspected it? Old fluid leaks can build up in it and mess up it's functioning. Pull it off and clean it in soapy water and it willl probably be as good as new.

Pedal going way down says you need to adjust your rear shoes. That's the only adjustment and where the only wear and changes in pedal travel can occur. So just adjust them. Be sure and do them properly per the book and not ignoring the parking brake involvement.
_________________
71 Superbug
71 Westy

[Wasted youth]

[udidwht]

[quote="Desertbusman"]Leave the booster on and remove the MC. If there is brake fluid in the booster the MC is shot.

I don't really understand how you are using you hand held vac pump. Unless you are using it from the hose connection at the engine then the check valve is fighting your test. FOrget about the hand pump and just use the vacuum from the running engine.


Also, have you pulled off the check valve and cleaned and inspected it? Old fluid leaks can build up in it and mess up it's functioning. Pull it off and clean it in soapy water and it willl probably be as good as new.

Pedal going way down says you need to adjust your rear shoes. That's the only adjustment and where the only wear and changes in pedal travel can occur. So just adjust them. Be sure and do them properly per the book and not ignoring the parking brake involvement.[/ mmquote]




How much travel? Bleeding the fronts will allow for the extra travel until he pumps them up.

I do it as such with helper...

Down...up...down...up...down...up...down slowly... Up...done. Next then repeat.
_________________
1972 Westy Hardtop/Type-4 2056cc
96mm Biral AA P/C's~7.8:1CR
Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
71mm Stroke
73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
Bosch W8CC plugs
Pertronix Flamethrower 40K coil
S&S 4-1 w/Walker QP 17862
3 rib 002 Trans
185R14 Hankook tires

[tristessa]

I'm not sure I'd bother trying to rebuild the existing master, but OTOH I'd be leery of the Brazilian stuff out there -- it was a 5-year-old Brazilian master that failed on mine. My comment about the "German" ATE being made in Czech Republic wasn't a complaint about quality, but about vendor inaccuracy re: country of origin. It's a beautiful MC and I wouldn't hesitate to use one again.

I used to work parts ten years ago, and we were getting some beautiful quality pieces out of Czech Republic, Slovakia and Slovenia .. dirt cheap. Way better than China and barely any more money.

[udidwht]

If I recall there is someone I believe in Texas who does top notch rebuilds on those MC's. Perhaps someone will recall the name.
_________________
1972 Westy Hardtop/Type-4 2056cc
96mm Biral AA P/C's~7.8:1CR
Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
71mm Stroke
73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
Bosch W8CC plugs
Pertronix Flamethrower 40K coil
S&S 4-1 w/Walker QP 17862
3 rib 002 Trans
185R14 Hankook tires

[Wasted youth]

Master cylinder pulled, servo unit partially filled with brake fluid. News at 11...

[jtauxe]