Bringing this back up as I've got some new information. The front calipers were replaced, all four wheels bled, and nothing but new brake fluid coming out. Front caliper definitely had gotten some air as a result of an boot that had unseated itself. The an now brakes smoothly and has noticeably less nose dive than before replacing the front calipers.

The parking brake still won't hold the van in place. The rear brakes seem to move farther when applying hydraulic brake as opposed to the parking brake (not by much), and with the wheels in the air the parking brake is enough to keep me from moving the wheels by hand. With the wheels on the ground, the brake is no match for the weight of the van. I tried winding the piston back out (maybe half a turn) and it improved the grip in the air, but on the ground still makes no difference. I must have engaged the parking brake 100+ times at this point.

Any ideas? (Aside from the immediate nuclear option of buying new calipers, which I'd like to avoid if possible, but will replace if it becomes necessary).

 

It turns out that both rear calipers failed in the same way at the same time (parking brake actuators failed simultaneously). Set me back $170 - $50 for a mechanic to confirm the issue since I wasn't entirely sure, and $120 for two new calipers. What was supposed to be a $230 pad, rotor, and fluid exchange job turned into a $600 complete hardware overhaul (passenger front caliper had a boot separating from the base of the caliper, so both fronts had to be swapped out too). And then throw in another $90 for a propane tank ($50 since it was brand new and I I have no other need for propane - charcoal all the way!!) and heater (40) - it was 20 degrees F here today with a wind chill at 10. I did the front calipers last weekend, and found out this week that the back were definitely shot and needed to be replaced.

If anyone eve needs to replace the LD rear calipers, the real trick is getting he parking brake cable out. You need three hands to release the retaining clip that holds the cable in place. Thinking about it now, a cable tie placed around the retaining clip would probably allow the job to go faster - it would hold the three arms down , but still slide forward when you pull the old caliper off. Disconnect the brake hose first - much twisting is involved, and you simply can't get it in the right spot while everything else is still connected. Installation was easy - attach the cable to the actuator arm, pull, and bring the notch in the cable arm over the cable - the springs involved in the rest of he he system will do the rest of the work for you.

 

Having gone through the rear caliper replace (frozen, burned up) on my 2011 and experienced the "needing to be an octopus" to remove the cable, the tie-wrap sounds like a great idea. I tried a few of those gadgets designed to remove quick disconnect fuel lines but none of them fit right. Thanks for the suggestion. I'm sure I'll be doing calipers at some point on my new to me 2012.