The Stovebolt Site Forums The Shop Area Driveline Front Disc Brake conversion problem

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.

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.

Make sure the rod from the linkage to the M/C is adjusted properly. Seems the proper adjustment is very critical.🛠

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

Exactly what I was thinking. Hope it is an easy fix! Will first check for binding.

Thanks Fellas

I had the same issue, in my case it was the master ctylinder rod adjustment.
don

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.

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

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?

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

DADS50

You and I are on the same page. My brake pedal will not fully return and therefore causes the brake light switch to stay activated. This happened early on and ran my battery down. Now I at least know to check before parking the truck for an extended period. Doing my paying job today. Perhaps the wife can help me a little with diagnostics tomorrow.

Thanks for your assistance.

John

I had to add brake pedal return springs so the brake lights would go off.

I have a spring but still lift up on the bottom of the brake peddle when shifting to ensure the light stays off

I have a BIG brake pedal return spring and getting really tired of having to reach down and lift up on the brake pedal to not only make sure the brake lights are off, but to release the brakes from them staying partially engaged. Not a very fun drive nor is it safe.

John in NC

How does the alignment look between the mc and the brake pedal attachment?


Do you have a pic you can post?

If you can make the brakes function normally by pulling up on the pedal with your toe, common sense dictates that you need a stronger pedal return spring. There should be NO contact between the pedal linkage and the master cylinder or the booster plunger before the pedal travels at least a healthy fraction of an inch- - - - -just like a clutch pedal.
Jerry

I had the same problem with my power brake system under the floor, and had to replace the new booster as it was defective out of the box. Adding a bigger spring did not consistently solve the problem. If yours is power brakes they probably need to replace the vacuum booster. The new booster solved the problem completely for me.

Mark

Also make sure the pedal isn't dragging on the floor board, floor mat or carpet. I had the carpet pad get pinched in the floor board pedal hole cause that same problem...

Mike B

I believe my problem is with the booster. Plenty of room around the pedal to not get stuck on the firewall, no carpet to get caught on and only the thin rubber floor mat. It seems to have progressively gotten worse since we picked up the truck in October.

My restoration included having disc brakes with a power brake booster installed for the front brakes only. I stayed with drum brakes on the rear. Just wondering if anyone has installed a #5559BB from Classic Performance Products, Inc. and how it worked or didn't work for you.

Thanks,

John