I got the 1979 Pontiac Catalina to start and run last weekend, so I paid $730 for it today. For a 42 year old car that's sat outside in Ohio almost all of its life, it has surprisingly little rust! I did encounter an issue when we were attempting to move the car today. The front caliper brake pins seized, so the pads were frozen to the rotors. The car will go into gear and hunches the rear end down when you give it gas, but it will not roll because of the front brakes. The calipers do not slide back and forth on the guide pins. I drenched the driver's brake assembly with brake cleaner and soaked it in PB Blaster. I put the wheel back on about an hour later to get it off the jackstand, and while tightening the wheel with the tire iron, the tire started to spin again. Do these calipers sound salvageable, or are they pretty much shot?
Also, what size Allen wrench do those pins need to back them out? They have Allen key holes, not hex heads like a modern caliper, which confused the crap out of me. This car has completely forced me to relearn the way with cars, I grew up with modern fuel injected cars and have never gotten my hands on an old school vehicle like this. It's 12 years older than I am, haha.
Well you're in for an adventure if all you've worked with are modern cars!
I would assume the calipers are shot. For that matter you'll want to go through the entire hydraulic system. Certainly if brake hoses are original they need to be replaced as well. Parts should be cheap and readily available. (If you haven't had the pleasure of working with drum brakes you're in for a "treat" when you get to the rear wheels!)
I'm not sure what size allen wrench you need for those caliper pins. Over the years I've seen sizes like 3/8", 5/16", and 8mm.
Oh I've encountered drum brakes before, and I don't look forward to messing with them again, haha. I replaced the shoes in the rear end of my 1999 Ford Ranger and that was a nightmare, both from my own inexperience with them, and people at the local auto parts stores giving me the wrong hardware. It was a 24 hour adventure, but I got it all back together. Even opened them up again 10 months later to rip out the rusted parking brake cable after asking Scotty why my parking brake stuck on one side. It all works like new again.
Yeah, drum brakes are awful to work on! Wrestling with brake springs and adjusters is not my idea of a good time. Just replace everything in there so hopefully you won't have to mess with them again for a while. Be sure to lube the brake shoe contact points on the backing plates. You can use disk brake caliper grease for that. (Hopefully they are not already worn down. If those are shot the shoes won't be properly aligned no matter what you do.)
It probably isn't worth trying to revive the calipers. Being a GM product it may still be fairly easy to find a set of calipers for it.
I noticed when I was pressing on the brake of the Catalina that the pedal does not firm up if you repeatedly press on the pedal and the engine is off. I saw what looks like a trickle of fluid from the connection between the brake master cylinder and the booster, which might mean the cylinder is leaking. Would it be worth changing out as preventative maintenance while I'm revitalizing the brakes? I feel like the pedal not firming up might also be an indicator that the booster is worn as well.
If the master cylinder is leaking it will damage the brake booster so I'd definitely swap that out. (Not to mention of course if the master fails badly enough you could lose the brakes entirely.) On a vehicle that old every part of the hydraulic system would be suspect.
I dug into the system a bit more today, the reservoir has two separate chambers, a front and rear one. The rear chamber is low, popped on the brake light, and the front is around normal. Is that an indicator that a rear line or wheel cylinder has popped?
Most likely. Look for traces of brake fluid on the inside of the rear tires. There's a very good chance that one or both wheel cylinders on the rear drum brakes are leaking. On a car that old the rubber brake hose going to the rear axle will also be suspect. Steel brake lines can also corrode and leak. (I recommend NiCopp line to replace rusted steel lines. Very easy to bend and flare.)