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Discussion Topic:
40 Deluxe brake system question
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2manybikes |
12-17-2021 @ 2:52 PM
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Member
Posts: 39
Joined: Sep 2021
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The brake pedel comes up to the top from about the halfway point as I drive the car eventually turning the brake lights on. It did this before adding the Boling Brothers drum brake conversation as well. After it sits about 40 minutes the pedel drops and the brake lights go off. It will do this in less than 15 miles. Checked the tire rotation this morning and there was no unusual drag from the shoes but I loosened them up anyway. 15 miles or so and the same thing. I have a gravel drive with a downhill slope off the main road so I turned in going a little faster than I normally would and pushed in the clutch, none of the wheels locked up in the gravel. I hit the brakes hard and started skidding, the brakes were definately not locked up. At the house I checked for unusual heat on the rims, nada. No hot brake odor or smoke. I'm out of ideas other than replacing the master cylinder but I don't like throwing parts at a problem before I know what it is. I'll open this up to the experts! Thanks.
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alanwoodieman |
12-17-2021 @ 3:38 PM
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Senior
Posts: 868
Joined: Oct 2009
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pedal return spring OK, and brake rod clearance is good?
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2manybikes |
12-17-2021 @ 3:46 PM
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Member
Posts: 39
Joined: Sep 2021
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Both re OK.
This message was edited by 2manybikes on 12-17-21 @ 3:48 PM
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TomO |
12-19-2021 @ 10:09 AM
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Senior
Posts: 7256
Joined: Oct 2009
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It sounds like you do not have the correct pedal free play. Without the 1/4" - 3/8" pedal free play, measured at the pedal, the piston will not return enough to uncover the fluid return port in the master cylinder. I like to adjust it by listening for the push rod to hit the piston and then check the pedal movement.
Tom
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2manybikes |
12-19-2021 @ 1:05 PM
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Posts: 39
Joined: Sep 2021
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Thanks for your reply and suggestions. I'll back it off a little more and see what happens.
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2manybikes |
12-26-2021 @ 6:53 PM
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Posts: 39
Joined: Sep 2021
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I'll admit to not being much of a mechanic, so I'm going to ask. Is there any adjustment to the brake pedal other where the rod enters the master cylinder? If thats it, does moving the nut and lock nut away from the master cylinder put more "play" in the travel? Still trying to figure out if the adjustment is too tight or if the master cylinder is the reason for my initial post. I backed it off about 1/8" yesterday and I'm still having the same problem. I can back it off more, but want to make sure I'm going in the right direction.
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kubes40 |
12-27-2021 @ 8:08 AM
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Senior
Posts: 3406
Joined: Oct 2009
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TomO is spot o with his advice. Your issue with the brake lights comes from the rod at the master cylinder being too long in adjustment. There is a fine line between "correct" and too long / too short. Creep up on the adjustment. Low pedal? Brake shoe adjustment... figure about .005" clearance at BOTH the top and bottom of each shoe. Arcing shoes is paramount to a properly operating brake system.
Mike "Kube" Kubarth
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TomO |
12-27-2021 @ 8:36 AM
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Senior
Posts: 7256
Joined: Oct 2009
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You need to shorten the distance between the brake pedal and the master cylinder, so you would turn the push rod in the direction that would make the rod shorter, the nut would go away from the master cylinder. Here are 2 pages from the training manual showing what you are trying to accomplish and how to do it. When I am under the car, I reach up and try to pull the pedal down slowly. If there is any clearance, you can hear the click as the pushrod hits the piston. If you don't hear the click, shorten the rod about 5 turns and then listen for the click. If you can't hear it try to feel the movement before the rod hits the piston. You are looking for 1/4" - 1/2" movement at the top of the pedal before the rod touches the piston. I hope that I have cleared up your questions, if not I will try again. Tom
This message was edited by TomO on 12-27-21 @ 8:48 AM
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2manybikes |
12-27-2021 @ 9:04 AM
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Member
Posts: 39
Joined: Sep 2021
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kubes40 and TomO, thanks for the additional info and clarification. TomO, Thanks for the service manual pics, that helps too. I need to get some general repair info. The weather is supposed to be really nice tomorrow so its back under the car!
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40 Coupe |
12-28-2021 @ 5:36 AM
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Senior
Posts: 1678
Joined: Oct 2009
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The brake pedal return spring must be missing or broken. With the proper spring in place the brake pedal should always return all the way and should not move by itself.
This message was edited by 40 Coupe on 12-28-21 @ 5:52 AM
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