rear brakes on a 78 - frozen pistons

[timspider]

I know there are many threads on the rear brakes, as I found a lot of good stuff in there. I've got this boiled down to one or two questions, I think.
I have a 78
Got the calipers and rotors off easily. Waiting on new rotors and cleaning and prepping the calipers so it's a quick install when rotors arrive.
Pistons on both sides look good, no rust, clean, the rubber boots cleaned up nicely. Calipers nice bare metal.

I can't seem to get these pistons to push back in. Took cap off of brake fluid reservoir to allow fluid to push back into it.
Can't use a C clamp because I don't want to squeeze on that outside portion of the caliper. Found a way to use a bolt and washer through a small metal plate, pushing on one of the old pads I put back in place. I can get plenty of pressure on it with this, but no visible movement.
I do have the back jacked up and noticed from a thread that the rear end must be loaded, so jacked up the rear in the middle and "loaded" it, but no difference.
I saw that these do not go all the way in like the fronts, one guy said they stick out 1/16 of an inch. Mine are both sticking out a good quarter of an inch at least.
Is there anything else I can/should try before going the "rebuild" or "replace" route?
Budget means that will delay this for even longer.

[timspider]

My main question: I see references to "turning" these, using a blade of some sort in that groove in the piston.Is that how I am supposed to push these in? By screwing them in rather than just pushing them in?

[wizard124]

My main question: I see references to "turning" these, using a blade of some sort in that groove in the piston.Is that how I am supposed to push these in? By screwing them in rather than just pushing them in?

Both pistons are standard thread.

[timspider]

OK, but do they screw in to re set them for new pads or do they push in?
I don't get how they could freely travel when you brake if they have to be screwed to move.
Or maybe I'm screwed. Not sure. Need to make sense of this.

[wizard124]

Both. The caliper needs to be screwed down as far as possible on the threaded shaft and compressed by pushing on the caliper. You may need to open the bleed screw.

The slot needs to be positioned pointing towards the center of the rotor to accept the ridge built into the back of the disc pad.

[timspider]

thank you. bleed screw gives me something else to try today and thanks for the whole turning pic and explanation. Maybe I'll get calipers loaded today.

[bobplyler]

I've never had to use the bleed screw when installing rear pads. Just screwing in the piston works.

[DieselSpider]

OK, but do they screw in to re set them for new pads or do they push in?
I don't get how they could freely travel when you brake if they have to be screwed to move.
Or maybe I'm screwed. Not sure. Need to make sense of this.

The screw is part of the auto adjuster for the parking brake actuator with the other half inside the piston itself. When you screw the piston down on it you are basically setting the auto adjuster in the starting position for new pads. The spring in the parking brake mechanism is not so stiff that it prevents the brakes from working.

[timspider]

that helps. makes sense. now back to the barn for some screwing. wait.., that sounded bad.
thank you

[4uall]

[timspider]

laughing for two reasons- one is the baaaaa image and the other is that using exactly the method described, with a little vice grip added and my boot wedged next to the vice grip to hold caliper, I was able to get these babies turned with a file and a big ol pliers as shown.
giggle.
thanks much- relieved that I don't have to replace of re build these.
as they say on set, moving on.

[timspider]

ok, not so fast mr. moving on.
I've got both turning pretty well. So hopefully my last question on this part.
Are these threads super fine? So it takes many turns to see a tiny move?
Or do I need to also exert down pressure while turning to get them to retract?
Got 2 full turns on both. Is there a general number of turns to re set these? Like 5 turns or more?
I remember seeing that they do not go flush, but leave a 16th gap. True? Am I dreamin?
Do I go until they feel bottomed out?
Push while turning?
Any danger of turning too far?
not one question, I know.
Thank you

[timspider]

sorry- I think wizard already answered this above- sorry, getting antsy to get past this.
back to the barn

[DieselSpider]

There is a directional clutch inside the piston on the self adjuster that locks to screw out and slips after moderate force is applied when screwing it in. If the threaded stud is badly gummed up or corroded then it may bind things enough to cause the clutch to slip preventing the piston from screwing in at which point a rebuild kit would be in order. If the fluid has not been flushed every year or two it can become corrosive enough to bind things up and cause problems. As long as the piston is not badly pitted the Akron kits are pretty complete having all the seals required including the one for the parking brake actuator and at less than $8 are a good deal having the seals to rebuild two calipers.

[timspider]

this MIGHT actually be my last question. got both retracted, although I'm not really sure what fully retracted should look like.
My rotors came this morning so I went out the barn to try to install the one that retracted a little less thinking if the new pads fit in this one, we are good to go.
Got the cleaned up caliper re-mounted, new springs in, pads in, and voila, the caliper did fit, with a little bit of rubbing.
The wheel turns, but not completely freely. You can feel the drag a little. I'm guessing this is the kind of drag that you would not notice when driving, and hoping that as I get the new pads bedded, it will lessen.
The question:
Is a little drag on the rotor normal when you install brand new pads?
Or should the wheel spin completely freely right off the bat?
Thanks again- moving on to new clutch and tranny next- look for posts around that unless I have my stuff together more than I think.