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Front Disc Brake conversion problem
#1349555 Wed Mar 11 2020 02:30 PM
Joined: Jun 2005
Posts: 484
R
Shop Shark
I have a 1958 Apache 3100, fully restored, including a Disc Brake conversion for the front axle. Kept drum brakes on the rear. The master cylinder, etc. is mounted below the driver side floorboard. The problem is not that the truck doesn't stop, when I depress the brake pedal, the pedal does not release all the way, will not disengage the brake light switch, causes the brakes to drag and requires me to have to reach down and lift up on the pedal to get the brakes to release. This is very unsafe and not the way I want to enjoy this truck.

Any ideas as to what the problem is and more important how to correct it? The restoration shop that did the brake install with all the rest of the work installed a really big spring to get the pedal to release, but that ain't helping.

Re: Front Disc Brake conversion problem
raleigh58 #1349556 Wed Mar 11 2020 02:40 PM
Joined: Feb 2000
Posts: 4,128
J
Shop Shark
The master cylinder should have enough spring to push the pedal back, if you have a power booster, it could be faulty. Also check all the pivot points of the brake lever and make sure it's not dragging on something. If you are using a pressure sensing switch for the brake lights, they turn on the lights at very little pressure. My truck would hold the lights on with just the weight of the pedal after stopping. I replaced the switch with an electronic micro switch, I got tired of pulling the pedal up with my foot. I also tried a spring to pull up on the pedal, it didn't help much.

Re: Front Disc Brake conversion problem
raleigh58 #1349558 Wed Mar 11 2020 02:41 PM
Joined: Apr 2005
Posts: 8,662
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Make sure the rod from the linkage to the M/C is adjusted properly. Seems the proper adjustment is very critical.šŸ› 


Martin
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Re: Front Disc Brake conversion problem
raleigh58 #1349563 Wed Mar 11 2020 03:27 PM
Joined: Apr 2005
Posts: 1,739
R
Shop Shark
I have installed several of the under floor conversion kits. I discovered that the large pivot pin that connects to the pedal and the linkage was oversize and would bind up. I subsequently used the original pin and everything worked OK. I'm not sure this is your problem but it is a possibility.
Fred

Re: Front Disc Brake conversion problem
raleigh58 #1349567 Wed Mar 11 2020 03:40 PM
Joined: Jun 2005
Posts: 484
R
Shop Shark
Exactly what I was thinking. Hope it is an easy fix! Will first check for binding.

Thanks Fellas

Re: Front Disc Brake conversion problem
raleigh58 #1349689 Thu Mar 12 2020 02:14 PM
Joined: Jan 2000
Posts: 550
D
Shop Shark
I had the same issue, in my case it was the master ctylinder rod adjustment.
don

Re: Front Disc Brake conversion problem
Donsz #1349695 Thu Mar 12 2020 02:52 PM
Joined: Jun 2005
Posts: 484
R
Shop Shark
Thanks Don. I had an independent garage look at it and that was one thing they were looking at, but still could not solve my issue. So, the truck is headed back to the restoration shop that installed the new front brake system.

Re: Front Disc Brake conversion problem
raleigh58 #1349698 Thu Mar 12 2020 03:09 PM
Joined: Jan 2010
Posts: 4,511
D
Shop Shark
Will the pedal return if you disconnect the yoke?

This test might tell you if your return springs work properly.

I did have to use a different pusher rod on my m.c. I use a manual master cylinder


Re: Front Disc Brake conversion problem
raleigh58 #1349733 Thu Mar 12 2020 08:25 PM
Joined: Jun 2005
Posts: 484
R
Shop Shark
Dads50,

So to check the spring function, I should disconnect the yoke, have some one depress the brake pedal and me underneath the truck to watch and see if the pedal returns all the way to the "up" or fully released position. Assuming the pedal returns all the way and disengages the brake lights, that should tell me what, the spring is sufficient and there is a fault with the master cylinder?

If the master cylinder plunger does not fully return is there a fix for that or must the entire master cylinder be removed and replaced with a new one requiring bleeding of all the brake lines?

Re: Front Disc Brake conversion problem
raleigh58 #1349735 Thu Mar 12 2020 09:00 PM
Joined: Jan 2010
Posts: 4,511
D
Shop Shark
Thats what I was curious about

As a test a few years ago I removed the return springs, A member on this board speculated that you should not need return spring. That the MC would return the pedal.
This was incorrect.

The return spring was needed to activate the stop,switch arm.
When I did this test the brake light stayed on.

Sounds like your issue is with the MC.
But the brake pedal should still return

Just a troubleshooting suggestion

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