The job for the weekend was a combination of light body work and servicing the rear brakes. First came the brakes, which were frozen stuck. The piston was being held up by corrosion, especially in one brake where the previous assembly had installed the seal incorrectly and let debris and moisture in. Both calipers had torn boots and a lack of adequate grease.
In order to free things up I let both calipers spend the night in a can of parts cleaner. This removed old grease and grime from each, but did little to free the pistons. I removed the piston seal and set each upright in a vise, then filled the little well in between the piston and the sealing well with a 50:50 combination of transmission fluid and acetone. If you don’t know about using this combo as a penetrating oil, read this: http://www.jalopyjournal.com/forum/threads/penetrating-oil-showdown.350800/
After sitting overnight I cleaned them up and worked the hand brake lever; a few cranks and they were moving. If you are rebuilding rear calipers on a FIAT remember a couple of things: The pistons are screwed onto a shaft inside the caliper and, upon reassembly, the fine line etched into the piston needs to face the bleed / hose side of the caliper.
I have two calipers of different makes – one is the OEM FIAT caliper (left) and one is an aftermarket one from Bendix. I believe Bendix was one of the manufacturers for FIAT; regardless, they are identical with the exception that one is right and one is left. And yes, that’s an IKEA wrench I pulled from my drawer of 1,000 wrenches.
Removing the handbrake mechanism involves removing this little circlip and pressing out the rod. It is very easy to press out and hand pressure may be adequate. A hard metal shim fits in the slot on the rod. The shim presses against the caliper piston rod, activating the hand brake.
Once disassembled the brake reveals its simplicity. Notable are the washers round the caliper piston rod – they have an order to them that creates tension. The order is shown above, from the base (piston end) of the rod they are convex-concave-convex-concave-convex-concave or like this: PISTON –()()()–] HAND BRAKE
Another view of the hand brake assembly with the rod partially extracted. I use a 1000 grit sandpaper on the rod and piston, a brass brush (on a dremel tool) on everything else, including the piston bore. This gets rid of the corrosion. There is no need to hone these, though it wouldn’t hurt as a cleaning exercise, as the piston does not ride on the bore walls. Corroded walls can certainly affect movement, but all they need to be is smooth.
Finally, some light filler on some low points in the body. The hideous green was a way to do a guide code where the low spots were very clean – on a brown car the sanded color of the clear coat is nearly the same color as the primer I used for a guide coat initially. Green saved the day. It looks a lot thicker in this picture than it really is. Otherwise these dings are almost the only ones on the car, I’m using Evercoat Rage 105 and the maximum depth thus far is about 2mm. See the filler on the sail? Ass dents from people sitting up there…don’t sit on the sail!