Does the parking brake apply both wheels?
This is from the deep recesses of my memory but the original cherokees had no toe brakes at all. Just the handbrake. When they added toe brakes they routed everything through the handbrake cylinder so it's between the toe brakes and the brake cylinders. So you have to bleed the handbrake as well as the toe brakes and if a seal in the hand brake is gone you may get these symptoms...
I also may have missed it but don't see where you've checked if the caliper at the wheel needs new seals?
I also second the people say saying follow the lines and look for leaks. I spent all afternoon once trying to get a 182 bled and it'd be good and then 20 minutes later it'd be spongy again... finally found the pinhole seep I'm the rubber lines beneath the floor.
Yeah, your recollection matches mine. I think the original Cherokee stole a bunch of stuff from the Tripacer, which also just had the single hand brake and the overhead crank for the trim.
What I remember, and it’s been the better part of a decade since I touched a Cherokee, is that you had a couple factors that made them such a bitch to bleed.
1. Sheer number of parts in the system. 5 master cylinders vs 2 in, say, a 207, made a lot more places for things to go wrong (although several of ours had no brakes on the copilots side).
2. Use of -4 hose/tubing for brakes vs -3 in similar Cessnas meant you had to move (if I’m mathing right) over twice the volume of fluid to get a good bleed.
3. Arrangement of said 3-5 master cylinders, especially the 5 cylinder setups, meant you could have a stubborn bubble that would just bounce back and forth between sides.
3 (a) the installation of the toe brake cylinders was sort of “upside down” and sometimes you had to take them loose and flip them around to get a stubborn bubble out.
4. The design of the toe cylinders with the parking brake meant that if you had wear on the shaft for the master cylinder, it could suck air in, which then could get pumped into the rest of the system when using the parking brake. The shaft on a Cessna could be worn clean out and it wouldn’t matter with the reservoir being mounted right on it and the different parking brake design.
Your typical SE Cessna brake system is just so much simpler and easier to work with.
Like I said this is just the highlights that I remember. The upshot of it is that ANYWHERE that shows a fluid leak in the system is also a place it could pull air in and you need to start with tracking down and fixing all of those first.