Refurbish (not rebuild) 308 rear calipers

I've been working my way through the 1984 Euro 308 GTS QV that I purchased last July, taking car of all the maintenance and overdue maintenance through the winter. Heater and coolant hoses, fuel lines, Ferraripilot aluminum radiator, plugs, wires, injectors, etc. etc. I'm planning to finish the Spring work with replacing the water pump, checking valve clearances, and changing the timing belts and tensioner bearings - and check the cam seals to see if the front upper oil leak is the cam cover gasket or front exhaust cam seal.

First, though, I am finishing the brakes. I've been installing the Goodridge braided teflon lines to replace the original rubber hoses, Porterfield R4S pads, on Superformance rotors. Aside from the nearly impossible task of removing the inboard end of the rubber brake lines (and equally nearly impossible task of tightening the new braided lines), the front brakes were not too bad to do - I cleaned the calipers up a bit, bolted on the new rotors, pushed back the pistons, installed the new pads, done!

The rears are a bit trickier, though. I've been using a few threads here and there for reference:
Birdman's excellent Rear Caliper Rebuild, Ferrari 308 and Replacing Ferrari 308 brake pads
Eric Shea's http://www.ferrarichat.com/forum/308-328/304911-dino-308-rear-caliper-rebuild-thread.html
http://www.ferrarichat.com/forum/technical-q/67429-retracting-piston-brake-pad-replacement.html
And a useful Pelican article Pelican Technical Article: 914 Caliper Rebuild

In general, it seemed the sentiment was that if the caliper is leaking anywhere, it needs to be stripped apart and rebuilt. At the easy end of the scale, simple worn pads only require a pad change and proper adjustment. I didn't find much written about what to do between these end points, though... My calipers were not leaking, but on removing the left rear pads I found that the outer pad was nearly worn out, less than 10% pad remaining, while the inner pad was about 70% remaining. Obviously the left rear brake was not fully functional, and if the inner pad was not wearing, it was not getting much pressure from the piston - and it would help explain why my handbrake was so useless that it would barely keep the car from blowing away on level ground if there was a strong wind.

After reading the rear caliper rebuild articles, I realized that I could clean up the pistons and bores without having to unbolt the caliper halves and install new seals. At least, that's what I took away from the articles linked above - I would appreciate comments and feedback from the experienced Ferrari mechanics and DIY crew as to whether this approach was reasonable, or if I should order the seal kits and pull them again!

Here's the right rear hub and caliper, with the pads already removed and the handbrake cable disconnected. The rotor was worn, with a very noticable ridge, so I had the Superformance rotor waiting to go in.

The rigid brake pipe from the hub bracket to the caliper was also removed at this point, to allow access to the two mounting bolts. Rather than mess with bending the hub bracket or unbolting it, I used a wobble extension on a socket through the hub bracket to access the top bolt - photo from above the caliper shows the 3/8 19mm socket and 3/8 drive wobble extension in place.

With the caliper removed, I removed the old rotor and cleaned up the hub so that it was ready for the new rotor. It should be apparent that I'm going for well maintained driving quality with my maintenance work, rather than like new or show quality - I'm not concerned with having all the parts replated, if I can clean off most of the grunge and verify the parts are OK to return to service then I'm happy.

Important note! Damp spots in the photos are not from brake fluid leaking out, they're from penetrating oil sprayed on the bolts, covers, bleed screws, flare connections, etc. a day or two in advance.
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Neither piston in the left rear caliper wanted to retract enough to allow the new brake pads to clear the new rotor. The caliper uses screw-type mechanisms on each piston to adjust the pad clearance to the rotor, so you can't just press or screw the pistons back in. While the adjusters were not frozen, they wouldn't pull the pistons back, so I decided to risk pushing the pistons out to see if I could clean them up without having to rebuild the whole caliper. This was successful - here's the outer piston removed from it's bore. It doesn't look too dirty, but it definitely needed a good cleanup. Since the seals weren't leaking before, I'm counting on them not leaking after. Even the dust boots on the caliper pistons were good, just a bit dirty.

Before cleaning, you can see the adjuster screw in the bore of the caliper, and the threaded piece in the back of the piston for the adjuster.
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The next photo was taken after the outer piston had been cleaned up and re-inserted into the bore. After the cleanup, the adjuster was able to retract it fully, giving clearance for the new pads!

Meanwhile, the inner piston has been adjusted out as far as the adjuster could move it, and was a bit of a struggle to remove. It was pretty grungy, with rust and dirt - no wonder it was siezed!
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After careful cleanup with brake cleaner and shop paper towels, the piston then looked like the "after" photo; and finally, with the piston lubed with brake fluid and carefully re-inserted and backed down, dust boots re-installed, the cleaned up caliper looks like the second photo. The dust seals over the pistons were in good shape, no rips, tears, so I just cleaned them a bit and reinstalled them.
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With the caliper bolted on, alignment shims on the bolts carefully restored to their original locations, handbrake cable connected, it was time to set the pad clearance. A feeler gauge of 0.004" is used on each side for the pad-rotor clearance, adjusted by using the 4mm allen key to drive the piston.
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On the outer piston, the adjusting screw has a 13mm lock nut to fix it once adjusted. It's supposed to be tricky to get the adjustment right and not have it shift when tightening the lock nut. There's a trick to make this easy - I have a pass-through socket set, which let me put the allen key through the socket while tightening the lock nut, eliminating the random movement of the adjusting screw. Very handy! It might seem that a simple 13 mm box wrench would be able to perform the same trick, but the lock nut is thin, not full height, and is recessed a bit below the outer surface of the caliper, just enough so that when it's snugged down there is not enough height of the nut above the plane of the caliper face to get a good hold with a box wrench.
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The first photo here is a view over the top of the caliper, showing the hard brake line now connected to the new Goodridge stainless flex hose.

Second photo shows the pad spring and pins back in place, done!

Third photo shows the cover over the outside adjusting screw. The inside pad is adjusted by the same 4mm allen key, but it turns a gear located under a cover with a 4mm allen key threaded cover.

After bleeding the caliper, I checked the handbrake function - to it's credit, with the handbrake pulled I wasn't able to turn the rotor. Whether it will resist the weight of the car with the wheel/tire mounted on the rotor remains to be seen, but at least the lever moves freely and the inner pad now presses on the rotor.
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Update - a couple of weeks after finishing the rear caliper cleanups, I noticed a few drops of blue brake fluid on the garage floor (I was using ATE Blue purchased last year before the ban on blue!). A bit of investigating found that the right rear caliper was dripping a bit. It wasn't the bleed screw or the rigid pipe, so it appeared to be dripping from the bottom of the handbrake lever shaft. I would guess that either a) I cleaned up dirt that was preventing a leak, or b) a seal started leaking when the pistons were fully retracted, a position they hadn't been in for many years, or c) used a bit too much brake cleaner and created a leaky seal on the handbrake lever shaft.

To make a long story short (and to leave it posted just once in this next thread) I bought new alloy replacement calipers (5 pounds lighter per caliper than OEM!) from PMB Performance, and am extremely pleased with them - price was $899 per pair on sale:

Here's the new thread where I went in to more detail about the decision to purchase, and more install photos: http://www.ferrarichat.com/forum/308-328/456055-review-pmb-performance-308-alloy-rear-brake-calipers.html#post143277155
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