Hello, All!
I screwed up when I installed a new MC and didn't bench bleed it. Have bled the brakes but pedal is still spongy so I suspect there is air in the MC. So question is, should I remove it from the car and start over, or is there another way to remove the air? What about a pressure bleeder like the kind that attaches to the reservoir cap? Will that remove air from the MC?
Thanks
With best regards, dukecola. E-mail: snipped-for-privacy@adelphia.net
I use a vacuum bleeder (manual, non-expensive one) on the vent valves. It not only does the same thing as a pressure bleeder, but it actually removes some, or all, of the air disolved in the brake fluid. "Boyle's Law for those who are interested!
Before I started using this method, my Beck Spyder had brake fade on the track from suspected boiling (air coming out of solution from the increase in temperature of the fluid), "Charles Law" for those who are interested! It is a cheap fix that is worth trying.
PS I did not bench bleed my MC either, and my pedal is tight!
Good luck and let me know how it worked.
Joe Gliebe
I seem to recall you can unscrew the master cylinder outlets and bleed the air out that way making sure the reservoir is kept topped up - can anyone corroborate this?
-Steve
Lacking a bleeder, you can do this: loosen the fittings on the M/C, including the stop light switches. Watch for fluid to drip out of all of them. Re-tighten. Now, bleed from the wheel cyls.
If you still get spongy pedal, it is caused by the fit of the shoes to the drum (I'll assume you replaced shoes).
Post back whether any work was done besides changing M/C.
Speedy Jim
Do you pump the MC after opeing the fittings or just let fluid drip?
Yes, I replaced the rear shoes. Haven't done the front yet.
Hello, Speedy! You wrote on Fri, 12 May 2006 19:24:24 GMT:
??>> Hello, All! ??>>
??>> I screwed up when I installed a new MC and didn't bench bleed it. ??>> Have bled the brakes but pedal is still spongy so I suspect there is ??>> air in the MC. So question is, should I remove it from the car and ??>> start over, or is there another way to remove the air? What about a ??>> pressure bleeder like the kind that attaches to the reservoir cap? ??>> Will that remove air from the MC? Thanks With best regards, dukecola. ??>> E-mail: snipped-for-privacy@adelphia.net
SJ> Lacking a bleeder, you can do this: SJ> loosen the fittings on the M/C, including the stop light switches. SJ> Watch for fluid to drip out of all of them. SJ> Re-tighten. SJ> Now, bleed from the wheel cyls.
SJ> If you still get spongy pedal, it is caused by the SJ> fit of the shoes to the drum (I'll assume you replaced shoes).
SJ> Post back whether any work was done besides changing M/C.
With best regards, dukecola. E-mail: snipped-for-privacy@adelphia.net
Don't need to pump, just drip.
New shoes only contact the old drums in a small contact area. When you apply pressure, the shoes actually "bend", trying to conform to the drum radius. This is usually the reason the pedal feels soft even after repeated bleeding.
The shoes will wear in after a few weeks; keep adjusting them.
Also possible that the adjusters are "backward". The slot for the shoe is beveled and will only work one way.
Jim
wrote
You don't need a fitting over the master cylinder. It goes over the fill reservoir.
in nearly 20 years of playing with vw's i've never bled a mastercylinder...just install then bleed from wheels....never had a problem...
Oooops! I meant to say over the brake fluid reservoir. Anyway, a long time ago I bought one of these pressure bleeders from the old Rocky Mountain Motorworks in Colorado. The screw on cap did not fit the brake fluid reservoir. I ordered the specific cap from the main company that makes the unit. Anyway, it works great!
Same
Installed master cylinder and bled from the wheels ...the furthurst one first.
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