Brake pedal doesn't bounce back

[patrickdotryan]

Hi guys. I did a full motor and engine bay rebuild. Tha involved a new master cylinder.

The issue I'm having is when I come back from driving I notice the brake lights are still on when I get out. The brake pedal hasn't bounced back so it is disengaged from the brake light switch. I have adjusted the switch up but that's not the issue. The pedal is just not easily returning to the up position. If I put my hand under and lift it up, it moves up several inches and engages the brake light switch.

Any thoughts as to why it's not retuning? I assume while I'm driving it's making everyone behind me think I'm riding the brakes too.

Cheers,
Patrick

[Russell J]

When I replaced my Master Cylinder, it came with two different length rods that connect from the brake pedal arm directly into the Master Cylinder.

Is it possible you are using the shorter rod?

[patrickdotryan]

Thanks Russell. That's a good question. My master cylinder came with one rod but because it was the same as the one I took out I used the old rod. Is there a reason why that might have been the wrong thing to do? Thanks. Patrick

[Russell J]

The old rod should work fine so long as it wasn't/isn't worn out, broken, bent etc. (which I'm sure you wouldn't have used it if so)

If you used the old rod, then maybe new Master Cylinder is the issue. You're sure it's the correct one?

In the end, the determination to be made is why is there less "push back" distance from the Master Cylinder to the rod to the brake pedal arm when you release the brake.

[patrickdotryan]

Thanks Russell. The old rod was working perfectly so I reused it. I have factory power brakes. The brakes work very well. I can stop the truck with just a light tap of my big toe. There is not an issue with pedal sink as there was air in the system. If I sit at a traffic light with my foot on the brake, the pedal maintains the right pressure.

When I first start the motor, the pedal drops with the vacuum of the booster. I believe it always did that and that's expected. It's that distance that the pedal drops that seems to leave some slack in the pedal when I turn the truck off. The spring used to return the pedal back up to the brake light switch. It seems like now that doesn't happen. Almost like the spring isn't overcoming the weight of the pedal. Just a very light lift with my hand and it comes back up.

Cheers,
Patrick

[TNIceWolf]

Crawl under the dash and take a close look at the rod connecting the brake pedal assembly to the brake booster. You may find that it is adjustable. It can be a bit of a PITA but may be able to solve your problem. My old F350 threw me that curve when I first bought it.

[patrickdotryan]

So I haven't solved this issue. however, I was driving along yesterday and this spring fell out on my foot. It seems like one end is broken so whatever its former use, it's probably not working anymore. Could this tiny spring be part of my pedal not returning issue? Anyone know where this spring goes?

image.jpeg

Love to know where it came from!

Patrick

[carnuck]

It could have been added but I recall one like that on the ebrake handle.

[Russell J]

Part 7A600 maybe?!

http://www.fordification.com/tech/image ... dals02.jpg

[patrickdotryan]

Oh wow. That's interesting. I'm traveling so can't look but I didn't notice that tab from memory. There is a lot going on in that drawing. From the drawing do you read it as all the setups have those tabs that has the spring notch? Mine is automatic and power brakes. Hoping that's it! Thank you for finding that.

[carnuck]

7a600 is the one I thought of. (left side of picture about 1/2 way down) which is on top of the ebrake assembly auto or stick. If you have one there, I know I added one to the '69 I used to have because the brake lights would come on after it sat a couple hours. If you shut it off and the pedal doesn't come up, try wiggling the checkvalve on your booster so the vacuum in the booster escapes. If it does, then the check valve may be clogged or swollen. If not the master cylinder may be rusty inside, the linkage may be rusty (pivot bushing or firewall adapter on some big block rigs with extra linkage) or the seals in the booster may be swollen. (time for rebuild)

[patrickdotryan]

Thanks carnack. I think I understand about the check valve but the pedal isn't stuck down due to vacuum or hydraulics. But I like the suggestions about the rod going through the booster. The booster is old and it did sit for a year. It works very well but maybe it is swollen and grabbing the rod if I understand correctly. The master cylinder is new but that doesn't mean it's good! Great tips. Thank you.

[carnuck]

Did the problem start right after the master cylinder swap? If so, the booster may not have had the adjustable rod inside or the master's pilot hole may be too deep.

With the pedal stuck down, loosen the 2 bolts holding the master to the booster a bit and see if it pops up.