New Brakes Frozen on First Trip

[Pete112]

Hi Everyone,

I finally got my '76 fully road worthy. I made an appointment with an alignment shop 30 miles away since the whole front end was rebuilt. This is also the longest journey the car has been on in who knows how many years.

When I bought the car 1 year ago, I replaced all the calipers, pads, master, and some of the lines. They seemed to work really well. I could easily rotate the wheels while in the air and when pressing the brake, they stopped rotating. So, the brakes seemed to work really well now and engaged properly.

Ok, so I'm driving along, and about 2/3 the way there or 20 miles from home, I could barely keep the car going forward. Yet the engine seemed to run fine. I pull over, get out, and the front wheels are smoking. It seems the front brakes were completely frozen. After I waited 10 mins, I called for a tow. By the time the tow arrived, the brakes did free up but I had it towed anyway since it was there.

Any clue what's wrong? The only thing I can think of is the adjustment rod inside the booster. I did adjust that before because the brakes barely engaged. The problem is, how much should I adjust it? If I adjust it much, it will take a lot of play before the brakes engage. Maybe it's something else?

Thanks for any help!

[narfire]

I can suggest there might be dirt or a small chunk of the seal that has broken off and when you pump the brakes to stop the piston moves forward to the rotor but the piston will nor retract I had this after a rebuild but only on one wheel. How are the flexable brake lines? You replaced some? Fronts?
There is a section on the IAP tech section that would help with adjusting the acorn nut in the brake booster
Good luck

[ClarkTheShark]

i had a similar thing happen to my car. a collapsed rubber line was my problem. but it was the center rubber line that hooks the rear end. seeing as how BOTH brakes are locking up in the front that leads me to believe that your problem may be in the master cylinder or booster. master cylinder is an easy rebuild and needs to be done anyways. i have never had problems with a booster.

[So Cal Mark]

since you adjusted the pushrod, my bet is that it isn't adjusted properly

[Pete112]

Yeah, the problem is definitely with both front brakes and yes both of those rubber lines are new. I imagine Mark is right since I did adjust it with no real knowledge that there was a proper way to adjust it. Like I said, I figured if the wheels spin easily with the car in the air and they stop spinning when you press the brake, you're good I guess that's not so true.

Master was replaced by PO only about a month before I got the car so it's new too. That's why I think the acorn needed adjustment. He replaced the master and the pedal went all the way to the floor. He was frustrated so sold the car to me. I thought finding the acorn was like hitting gold. Granted the calipers were shot too so his master solution wasn't going to work anyway.

I'll check out IAP's site.. thanks for the tip, and for any others before I hit up this project this weekend!

[manoa matt]

The specificaiton for the acorn nut adjustment on the IAP tech page is not the same specification as the Fiat Factory Manual, however there is some overlap in the specification.

IAP tech lists (0.825mm to 1.025mm) While the factory manual lists (1.035mm to 1.925mm)

The IAP booster is slightly different than the original, and may be the reason for the different spec.

I bought one a while back and adjusted the nut to 1mm past the face of the booster. I still have a somewhat soft pedal (car stops great despite), so maybe I need to adjust the acorn nut further.