Vacuum Brake Conversion Issues

[tomjon]

1st problem: Normal braking at best, no panic stop capability. On my '86 GN I used '86 N/A-6 master cylinder & booster (is this an OK unit to use?). Vacuum from vacuum block. New brake pads/shoes and all wheels bled. 2nd problem: Brake pedal slow to return, 4 - 5 seconds.

 

[~JM~]

Did you swap your brake pedal to a vacuum assist pedal?

I used the Master & Booster for an '87 Monte Carlo SS on my swap & it operates fine.

~JM~

 

[tomjon]

I used the proper pedal for the vacuum brakes. Should the master & booster come from a V8 car rather than the 6?

 

[Phatman]

Shouldn't make any difference....

 

[SuperSix]

Is it a new master cylinder?

 

[SS/GN]

Are the rear brakes adjusted properly?Seen this many many times

Kevin

 

[Nick Micale]

1st problem: Normal braking at best, no panic stop capability. On my '86 GN I used '86 N/A-6 master cylinder & booster (is this an OK unit to use?). Vacuum from vacuum block. New brake pads/shoes and all wheels bled. 2nd problem: Brake pedal slow to return, 4 - 5 seconds.

Having done more than 100 of these conversions using the same parts from the N/A Regal, they all have performed better than the PM, especially in a panic stop.

The most common problem I have found with guys doing this swap is the master cylinder was not properly bled. This will then introduce air into the lines which can cause problems like yours.

When doing this conversion it is not necessary to even bleed the wheel cylinders if the MC is bled and installed correctly.

My advise to you is to start over and bleed the MC and then each wheel cylinder. There is NO special procedure when bleeding this system, it is just like any of the earlier vintage GM cars.

If you need more help, call me as typing is NOT one of my skills.

 

[tomjon]

Thanks for the suggestions. I'll try the MC and wheel cylinder bleeding again. Any thoughts on the slow pedal return. No binding observed anywhere.