Just brought home a 67 with F disc. Brakes were very touchy on the test drive. On the way home the next day the rear brakes were smoking! Left it out front cause I wasn’t sure what was happening. Once it cooled done it was fine, no dragging. I thought maybe the brake hose to the rear end was old an swelling internally (had it happen on a Volvo) or the master or prop valve? Is this a common issue or do I need to test everything? Ugh! Still love the car but won’t take it out of the neighborhood just yet.
A lot of mechanics do not know or are unwilling to learn how to work on drum brakes properly. There are any number of things that could cause what you describe, but improper maintenance technique would be at the top of the list. I would put the car up on jackstands and remove the rear drums to see what level of mistakes are present. Swapped adjusters, mis - installed shoes, broken or missing adjuster parts, wrong shoe size, wrong wheel cylinder size - that sort of thing is common to find. Compare what you see to what the factory shop manual shows.
And don’t assume anything about the quality of new parts. I had a rear brake drag after I replaced all four corners. It ended up being a ridge in the new wheel cylinder that would not let a piston fully retract. After that lesson I’ll ream (if needed) and hone the originals before buying new ones.
Thanks for the replys, and Oops I left out some info. (still in the same boat I suspect) I raised the car but was unable to remove the lug nuts with my impact. No problem I’ll get the wife to help. Well she mashed the pedal and the brakes would not hold the torque of my breaker bar. Now I’m not as strong as I use to be but something ain’t right. Like I said earlier still in the same boat but maybe that rings a bell?
I had a guy here in Tucson suggest I loosen the master cylinder from the booster and see if it still acts up. I get the idea behind it. To see if its holding residual pressure due to improper brake rod adj. Question is how much should I loosen it 1/8" 1/4"?
Might throw a rear brake hose on it as its cheap $50 ish for US made hose. Had that issue on a past project car. Anyway I’m disabled but somewhat capable but slow. Doing bodywork on a off topic project is taking all my energy but I keep thinking about this issue.
I’d just take it to a shop but hate to spend $100/hour + for a kid to toss parts at it when it could be an adj.
I’ve found the backing plate have groves worn into it by the shoes. There are 3 “flats” per shoe. These get worn & cause the shoes to sit in the rut & act up. Sometimes they get grabby, or they can hang up. I fill weld them & grind them flush. Lube w/ brake grease. As Royce stated many other things in the system can be of issue. New rear hose, and the pressure valve could also be of issue.