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Old 06-27-2018, 12:22 PM
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Brake pedal not fully returning.

Good day all. I've been following threads about the brake pedal not fully returning and have the same problem with my '32 Ford. My master cylinder and booster are located under the drivers floor. I've followed the advice given, and still have the problem. I've removed, cleaned and lubed the front calipers. Drained a little brake fluid from the master cylinder and added a return spring to the pedal. I have about an inch of play before the brakes start to engage. All seems well when first driven and no heat has built up. After driving and getting hot, I noticed brake drag. I can reach down and pull the pedal up and the car will roll free. As you know there is very little room under a '32. I'm running shorty headers and dual exhaust, ending at the rear axle. The driver side exhaust is very close to the booster and master cylinder. Could heat be causing this problem? I'm considering switching to a single exhaust with a cross-over and running the exhaust on the passenger side to eliminate heat. Any other ideas that might be causing this problem? Thanks for any advice. Everett.

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Old 06-27-2018, 06:57 PM
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brake pedal

On all my builds (pre 49) the M/C is under the floor and I run the exhaust to the pass. side to avoid unnecessary heat on the M/C. Somewhere around the trans tailshaft the exhaust can be crossed back. Sounds as if you could start with a larger spring. After driving the car 'till the brakes start to drag open a bleeder and see if you get fluid to pop out. If, say you do get it on the left front, try it on the right front too. If you get fluid to pop again then you have a similar problem on both sides. If you relieve the pressure on one side and get nothing from the other side then you know the problem is back at the M/C. Do the same for the rear. Hope I made it clear enough. If you determine it's in the M/C drive around with your foot under the pedal so that it can't cause pressure and see if the problem goes away. I assume the flex lines are new.
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Old 06-28-2018, 01:07 PM
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Thank you 39 Master. Yes, everything is new and my exhaust is mighty close to the master cylinder. I'll try your advice very soon. Say, if I do have pressure in the lines then the problem might be in the master cylinder correct? Thanks again, Everett.
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Old 06-28-2018, 03:23 PM
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Pedal not returning

Everett, Let us know what you find. It may help other people with the same problem.
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Old 06-29-2018, 01:39 AM
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It appears to me the problem is nothing more than a too weak return spring. If you can make the car roll free by picking up the brake pedal that appears to be the issue. If the spring is holding the pedal against the bottom of the floor, shortening the push rod slightly or using a thinner rubber seal under the floor may be worth looking at.

The key is the piston must come back far enough to uncover the hole to the reseviour to prevent pressure building from expansion of the fluid as it gets hot.

John
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Old 06-29-2018, 07:09 AM
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Something to consider is that the bushing in the brake pedal is getting hot and expanding. Some of the synthetic materials that are sometimes used for no lube bushings can have a large coefficient of expansion.

I remember many years ago an old and seasoned street rod builder telling me about having to ream a steering support bushing that he had made out of Teflon several sizes oversize because it was near the exhaust manifold. After the car got up to temp, the bushing would expand and cause enough drag on the steering shaft that it would not return to center after a turn. There was no problem when it was cold.
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Old 06-30-2018, 10:34 AM
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Thank you all. My return spring is the type you would use for a clutch pedal. Connected to the brake pedal and connected to my bell housing. Its quite stiff and thought I had corrected the problem. Lately we have been getting nasty thunderstorms daily, as soon as I get a weather break, I'll get out on the road and try all your suggestions. Will let yah know the outcome. Thanx, Everett.
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