1958 Cadillac Bendix brake Booster Problem

[dw-2]

 I installed a booster rebuild kit on my 1958 Cadillac Coupe DeVille, when I reinstalled the booster, and started the engine the brake pedal was pulled down to the floor. Any ideas on what I may have done wrong?

[J. Gomez]

Did you rebuild the M/C only, the power booster or both?

It yours a Bendix or Moraine?

The symptoms you are describing is the power piston is being pulled by the vacuum inside the booster. When the brake pedal is pressed (slight tap) the power piston on the booster opens the vacuum valve allowing vacuum to fill the rear of the booster chamber.  However the piston return spring tension should hold the plunger from applying pressure on the M/C.

Did you installed the large return spring on the rear of the piston or front?

If you removed the vacuum from the vacuum check valve, does the pedal goes to the floor?

More details would be needed to properly trouble shoot the issue.

Good luck..!

[dw-2]

I rebuilt the BENDIX master cylinder two years, but could not find a kit to rebuild the booster,at the time. since then the booster quit working, and I was able to locate a kit to rebuild the booster, but it didn't contain all the parts that I wanted to replace.  The original atmospheric poppet spring was not usable, so I modified another spring to replace it. Also, the diaphragm assembly was not included in the rebuild kit.  I assume that the mechanism that applied and releases the vacuum is not functioning but I'm at a loss to find out why.

[dw-2]

Does anybody where to find additional Bendix booster parts?

[dw-2]

After bleeding the master cylinder when vacuum is applied to the booster the pedal goes down about half way - till the brakes and fully locked. when the vacuum hose is unplugged the break booster disengages and releases the brakes, pedal returns to full height.  Any ideas what's wrong inside the booster?

[J. Gomez]

After bleeding the master cylinder when vacuum is applied to the booster the pedal goes down about half way - till the brakes and fully locked. when the vacuum hose is unplugged the break booster disengages and releases the brakes, pedal returns to full height.  Any ideas what's wrong inside the booster?

The symptoms seems to be with the power piston, possible the vacuum poppet is open or defective not allowing to close the port.

I’m not familiar with the internal of the Bendix unit, others who worked on this may chime in.

I’m attaching a 1956 Pontiac Bendix power brake section which may be of some help on troubleshooting and fixing yours.

Good luck..!

[dw-2]

Thanks, The internals of the booster are identical to the 58 Cadillac