Trying to figure out why my brake pedal won’t return to the normal position and brake lights staying on. This happens only after driving for a bit and warm up. After reading many of threads it all points to the brake booster or master cylinder. Found some really good info just not the answer to my specific problem. In y’alls opinions where should I start ?

 

Brake booster piston stuck? I assume the pedal stays down halfway or somewhere in between? Have you attempted to bleed all four brakes yet? I'd start with the easy steps like that first and then move onto replacing components after some investigation. Also check your vacuum line for breaks or dry rot going to the booster. Someone more common with this problem will chime in I'm sure those are just the first things that come to my mind

 

Yeah about half way. Have to raise it up every time I stop. Haven’t attempted anything yet just wanted to get opinions first, thanks.

 

If your truck has the bellcrank linkage between the firewall and the booster in the engine compartment. The pivots there will rust up and cause this problem, Check there.

 

Is this the bellcrank linkage ?

 

Tad bit more info: 77 F250 2WD, single piston calipers.

 

D7TZ-2455-C .. Power Brake Pedal / Marked: D7TA-NA / Obsolete

1977 F100 2WD with Power Brakes without Speed Control // 1977 F150/250/350 2WD A/T without Speed Control.

 

The previous owner of my truck had a bungy cord wrapped around the brake pedal to keep it up high enough to keep the brake light off.

Jess

 

What brake light, the ones incorporated in the tail lamps, or this little charmer?

Brake Pressure Differential Valve Warning Lamp Switch, lights up if the brake fluid is low. Sometimes the valve gets out of adjustment, so the light on the dash comes on... and stays on.

The switch can also fail, it threads into this valve that some peeps call a proportioning valve.

C8AZ-2B264-A .. Brake Pressure Differential Valve Warning Lamp Switch =1968/79 F100/350, Bronco, Econoline & 1968/69 FoMoCo Passenger Cars.

Obsolete, available NOS & from auto parts stores.

 

It was the one on the brake pedal arm, arm just needed to go up 1/8" to 3/16" to turn off the switch. I've got it sorted out now.

Jess

 

Thanks Numbers !

 

Not a bad idea with the cord but I really want to fix it eventually. How did you sort yours out ? What did it end up being if you don’t mind ?

 

I adjusted the brake switch. It has threads on the plunger.

Jess

 

Oh ok. Yeah I did do that, didn’t help. Thanks for the reply.

 

Yours certainly does not look like rust has ever been an issue under that hood F250C! Very nice condition.
But I would still maybe spray some penetrating lubricant on the linkage behind that bracket you show in your first pic. Just to see if it helps.

I don't know if they are metal-on-metal, or if there are bushings in the linkage that wear out. I would thing no to the bushings on a brake system, but I don't know and have not messed with one of these before.
Pedal pivot points can freeze up too when the plastic bushing wears out (which they do).
Boosters can fail, and that has been a subject lately with several different symptoms.
I suppose the multiple springs inside a master cylinder can rust and fail too. Never had that happen, but any spring can fail given time. And moisture does tend to hide inside a brake system. How does the fluid look? Ever changed it?

Sorry not much help.
Good luck.

Paul