Parking brake won't hold - help diagnose

[jcode68]

Helping my buddy solve an emergency brake problem on his 67 Fastback. He has 9 inch reaerend with factory drum brakes. The rear brakes are adjusted fine such that on jack stands, car running and in drive, he applies the brake pedal and the tires stop as they should. If he uses the emegency brake and pulls as far as it will extend, the tires don't even slow down, never mind stop. Now before you say just adjust the emergency brake cables, been there and done that.

1. Have removed all slack from the cables and no difference.
2. We have also verified that the cables are not stuck.
3. We remove the brake drum and actuate the e-brake handle and you can see the cable pulls on the e-brake lever on the backing plate and the shoes move outward. The issue is it doesn't seem to be using enough force to move the shoes enough to stop the wheels from turning.

A good friend of ours has a family garage where they have done hundreds of brake jobs and he could not diagnose the problem either. Aynone have some suggestions about what to check? Seems to me that the hydraulic slave wheel cylinders are working fine, but whatever mechanical mechanism is responsible for moving the e-brake is not applying enough force. Thanks in advance for any help.

 

[ga289stocker]

I'm fighting the opposite of you right now. Anyway i wanted to mention that after i had disconnected the equalizer rod bar from the threaded rod end and went to reconnect it i mistakenly put the threaded rod in the wrong hole on the equalizer bar and it was given me the same issue that you seem to have as I would have handle as far out as i could pull it and it would not slow the tires down any. I noticed the
other hole on rod and it was a night and day difference, my issue i think is I have rear disc's w/ self adjusting calipers that i'm missing w/ now, hope that helps.

 

[10secgoal]

Do you have a pick of the underside of the car ? If a rod is switched on older cars it will move the leverage point to where with no load it can move, but won't apply any force to speak of. 65-66's are real bad for that.

 

[jcode68]

It's funny you say this. I should have mentioned that the original bracket that is welded to the passenger floor board where the hook (for lack of a better word) connects to the cable is missing since the floors were replaced by the PO. So the hook is actually attached to a hole located in the bottom of the frame rail. I would say the current location is about 3 inches more toward the back than where the bracket should be located. I did think about this potentially being the cause, but then thought as long as the cable tightens, why would it matter? I guess a class in mechanical engineering would help .
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[ForceFed70]

Could be that he has a bit of a stretchy cable.

I'd adjust the ebrake cable even tighter, you'd be surprised at how tight it needs to be.

While on jack stands, adjust the brake cable to the point that it starts to drag on the wheels, then ease it off a bit. It's not uncommon to run out of adjustment and need to replace/modify the cables.

 

[mustangmike6996]

this is a dumb question but i must ask because i have seen it before... i know you said you had the drum off.. was there brake fluid leaking onto the shoes causing it to be slippery... just curious.

 

[jcode68]

this is a dumb question but i must ask because i have seen it before... i know you said you had the drum off.. was there brake fluid leaking onto the shoes causing it to be slippery... just curious.

Not a dumb question - no brake fluid and just in case the shoes were glazed over, they were swapped for new.

Anyone else have some input on whether or not the connection point for the "hook" could cause this problem?

 

[GNN60GT500]

Wait a minute!!!

Are you telling me the parking brakes are supposed to work on these cars!!!

Ive had some that pretended to work- but never had one that actually did.....

 

[mustangman1974]

I thought it was there for looks. I added about 4 inches of washers after replacing both cables and it still didn;t work. I figured Ford just added them for looks.

 

[jcode68]

My ebrake in my 68 works great, no problems at all really. Guess these old units are fickle.
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