brake pedal problem

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Al Pezzella
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brake pedal problem

Post by Al Pezzella »

I had the complete brake system rebuild by Karps, I have a problem, when you depress the pedal, at the first 1/2" of travel it binds a bit and then it depresses normal. I spoke to Karps about it but they said that they bench test everything before it goes out and they think that maybe it's a linkage problem. This problem only happens when the car is running and brake system is under vacuum. When the car is not running the pedal feels normal.
I was wondering if anyone has encountered same type of problem

BTW I had Richard Garre from Radcliff Motor phase in my distributors with the Pertronix igniters and he did a great job, the car runs perfect now.
afwrench
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Re: brake pedal problem

Post by afwrench »

Hi Al , glad to hear that the car is purring now.As for the brakes I would first disconnect the rod from the booster or pedal if possible and check for any binding.Without vacuum the stiffer pedal may be masking linkage binding.Not that anyone cant make a mistake but I had some work done by Karp and it was top shelf.Regards ,Mike your" tent partner"
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tyang
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Re: brake pedal problem

Post by tyang »

afwrench wrote:Hi Al , glad to hear that the car is purring now.As for the brakes I would first disconnect the rod from the booster or pedal if possible and check for any binding.Without vacuum the stiffer pedal may be masking linkage binding.Not that anyone cant make a mistake but I had some work done by Karp and it was top shelf.Regards ,Mike your" tent partner"
I believe there is an adjustment in the push rod between the M/C and the pedal assembly.Unfortunately, it's a royal PITA to get to because the booster has to come out. Was the push rod length changed when everything was apart?

Tom
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Re: brake pedal problem

Post by 250GT »

tyang wrote:
afwrench wrote:Hi Al , glad to hear that the car is purring now.As for the brakes I would first disconnect the rod from the booster or pedal if possible and check for any binding.Without vacuum the stiffer pedal may be masking linkage binding.Not that anyone cant make a mistake but I had some work done by Karp and it was top shelf.Regards ,Mike your" tent partner"
I believe there is an adjustment in the push rod between the M/C and the pedal assembly.Unfortunately, it's a royal PITA to get to because the booster has to come out. Was the push rod length changed when everything was apart?

Tom
Tom,
The pushrod can be adjust from the the big opening of the pedalbox on a carbridge it takes 5 min. no come out of anything.
Well at least at 250GT.

C.
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tyang
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Re: brake pedal problem

Post by tyang »

250GT wrote:
tyang wrote:
afwrench wrote:Hi Al , glad to hear that the car is purring now.As for the brakes I would first disconnect the rod from the booster or pedal if possible and check for any binding.Without vacuum the stiffer pedal may be masking linkage binding.Not that anyone cant make a mistake but I had some work done by Karp and it was top shelf.Regards ,Mike your" tent partner"
I believe there is an adjustment in the push rod between the M/C and the pedal assembly.Unfortunately, it's a royal PITA to get to because the booster has to come out. Was the push rod length changed when everything was apart?

Tom
Tom,
The pushrod can be adjust from the the big opening of the pedalbox on a carbridge it takes 5 min. no come out of anything.
Well at least at 250GT.
C.
This is a 330 with hung pedals. The pushrod sits behind the brake booster and its length is adjusted by removing it after the booster and M/C is removed.

Tom
'63 330 America #5053
Timo
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Re: brake pedal problem

Post by Timo »

tyang wrote: This is a 330 with hung pedals. The pushrod sits behind the brake booster and its length is adjusted by removing it after the booster and M/C is removed.

Tom
Tom,
are You really sure about this ? It doesn't seem make any sense to have brake push rod adjustment with booster/MC assembly removed. How would one know correct length ? I don't know 330's, but with Daytona for example, which also has "hung" pedals, adjustment is easily done under dash with everything intact.
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tyang
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Re: brake pedal problem

Post by tyang »

Timo wrote:
tyang wrote: This is a 330 with hung pedals. The pushrod sits behind the brake booster and its length is adjusted by removing it after the booster and M/C is removed.

Tom
Tom,
are You really sure about this ? It doesn't seem make any sense to have brake push rod adjustment with booster/MC assembly removed. How would one know correct length ? I don't know 330's, but with Daytona for example, which also has "hung" pedals, adjustment is easily done under dash with everything intact.
Hi Timo,

I'd have to look at Al's particular set up, but I seem to recall very little access to the pushrod in a 275 with a similar set up.We set the free play before mounting everything together. Taking a look up under the dash will show if the access is possible.

Tom
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tyang
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Re: brake pedal problem

Post by tyang »

Hi Timo,

I just looked at the 330 parts book and it refreshed my memory of the pushrod I'm talking about. There are two adjustable pushrods. One is behind the pedal, but I believe there is another adjustable pushrod behind the booster. The one behind the booster is the one that's a pain to get to.

Tom
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Al Pezzella
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Re: brake pedal problem

Post by Al Pezzella »

I would have to agree that the problem is in the linkage, I noticed that if you go from the accelerator to the brake with authority, the hang up is not there, but if you gently push on the brake it's there, also I noticed that on the up travel of the pedal there is a bit of a hang up at the same spot. I will try to work on the linkage this coming weekend and will let you know the outcome.
Thanks for the tips everyone.
Karps did the full system and they did a great job down to the plating.
8339
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Re: brake pedal problem

Post by 8339 »

Tom is correct, there are two push rods, one from the pedal to the booster and then the "booster push rod" that goes from the booster to the M/C. There should be zero clearance from the booster push rod to the M/C piston. Too tight and the brakes will self apply depending on vacuum, too much clearance and you'll never achieve full action in the M/C. You have to measure the distance from the M/C mounting base to the center of the M/C piston and then measure the distance of the booster push rod at rest. Once you've set the booster push rod, then you can adjust the pedal to booster rod for your personal taste. This is not an easy 15 minute job, once you have it set you should never have to mess with it again.

Al, If you're going to do this, pull the booster and M/C first, see how the pedal reacts with just the pedal push rod, make the pedal return spring isn't binding or doing something weird. You could even dis-connect the pedal push rod and see how your pedal reacts. You may also want to put the M/C in a vise and bench bleed it to see if it's binding. The way your pedal felt it was more mechanical in feel than booster or vacuum however. Let us know.


Richard Garre
Radcliffe Motorcar Company
Timo
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Re: brake pedal problem

Post by Timo »

8339 wrote:...there are two push rods, one from the pedal to the booster and then the "booster push rod" that goes from the booster to the M/C. ... Once you've set the booster push rod, .... This is not an easy 15 minute job, once you have it set you should never have to mess with it again.
This is quite common with most all similar set-ups, regardless of the car or brake/booster manufacturer and if the M.C. and Booster were rebuilt as an assembly by Ron (or Jeff ?), Booster-to-M.C. push rod had probably been adjusted appropriately at that time. But then again, sometimes (?) we all might make mistakes or overlook procedures. :)
Timo
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