HiPo with front disc brakes

Kliz_old · September 16, 2008 at 3:31 PM

I've just finished the restoration of a 66 HiPo GT convert. The entire brake system has been rebuilt, including the original Kelsey Hayes rear brake proportioner. When driving the car, the initial pedal push on stopping is spongy and travels about an inch past the accellerator pedal. If I pump the brake a second time, the pressure firms up considerably and stops at about even with the acc. pedal.

I don't think this is normal. Is there anything you all can suggest that might cause this before I start troubleshooting. I want to suspect a problem with the proportioner since I've heard these rebuilds are not always successful.

Thanks

Bill

hipo_p51_old · September 16, 2008 at 4:32 PM

assuming you have no leak and the system is full of fluid. i would try bleeding the brakes.

RalphJr · September 16, 2008 at 4:57 PM

Sounds like air in the lines to me.

I've always had to bleed new systems 2-3 times to get all the air out.

I've had good luck with a one man bleeder pump system, but works slower than the old "press - hold - release" buddy system with someone in the car pressing the pedal and you on the floor getting squirted with fluid!

Did you happen to use DOT 5 silicone fluid?

If you did it WILL take several bleeds to get it right.

C6ZZKGT · September 16, 2008 at 5:17 PM Official Post

I have found that sometimes just driving the car aound helps the disc calipers to self bleed.

-Fred-

round2K_old · September 16, 2008 at 6:12 PM

A spongy pedal is usually air, but it also sounds like you need to adjust the rear shoes up as well. You might check the rear shoe adjustment before you go through one more round of bleeding. The shoes are running out to meet the drums when you hit the pedal the first time, and they're already out there when you hit it the second time so there is less distance they have to travel resulting in less pedal travel.

Edited by - round2K on 09/16/2008 18:14:12

BoS_old · September 16, 2008 at 10:03 PM

Are the calipers correctly installed and on the correct side?

/Bo

Kliz_old · September 16, 2008 at 11:05 PM

Thanks for the input everyone.

I've put about 300+ miles on it and condition hasn't changed. I know the "knockouts" are still in the rear backing plates. If rears aren't self-adjusting, then this might be the problem.

This brings up a question. Why haven't "knockouts" been removed in 90K miles to make adjustments? Can adjustment be made by removing the wheel and drum? This may be the easiest way if one has no lift! I'll try tomorrow and let you all know.

Thanks again

Bill

CharlesTurner · September 17, 2008 at 7:32 AM

Sure, you could make adjustments by removing the drums. It's quite rare to see an original pair of backing plates with the knockout plugs still there.

round2K_old · September 17, 2008 at 3:03 PM

If you haven't had a lot of experience adjusting rear shoes without the benefit of the knockout access it is very likely you don't have them fully adjusted, particularly if you're relying on the self adjusters. Self adjusters need back and forth motion of the drum (backing up and going forward) to adjust and even then they don't always ratchet out like they should.

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