I rebuilt the front calipers on my '96 Audi

[moribundman]

... only because the passenger side dust boot had recently developed a crack (appeared to be caused by mechanical damage, not wear and tear). I didn't want to do just one side, so I did of course both sides in the front.

I put a ca 3"x4," 1/4" thick piece of aluminum in the caliper opposite the brake piston to "catch" it. I very slowly pumped the pedal, maybe 20 times, and the piston came out effortless and without force. A couple pumps before the piston was totally out, brake fluid started dripping. I had a pan under it, so no problem.

The piston seal came out easily with a toothpick and looked fine without any signs of shrinkage or brittleness.

I cleaned the piston and caliper. The piston was pretty big, about 2.6" diameter and 3" long. There were no grooves, scratches, scuff marks or corrosion on the piston or inside the caliper cylinder. Corrosion was limited to the exposed outer part of the piston beyond the dust boot.

The new piston seal simply popped in, and the piston boot was also easily installed -- when the piston is being pushed back in (which I could actually do by hand, didn't need my brake piston tool), the outer dust boot lip popped into the piston groove.

I didn't prefill the caliper, but I bled it without any issues with my pressure bleeder. I bled first only the front, then in the standard order (right rear, left rear, right front, left front).

I spent about 2 hours all in all.

At nine years old, this is the first time the calipers have been rebuilt. Looks like the OEM calipers will live as long as the car -- which is exactly what my old VW tech kept telling me.

I suppose I'll do the rear calipers in a couple months, just to be safe. A seal kit is only about $20.

PS: Castrol GT LMA DOT 4 went in.

 

[labman]

From the posts I see here, I think the warmer climates maybe friendlier to calipers than here in the salt belt. Yours sounds close to what I might expect for something a little newer. Even old neglected stuff, usually was fine inside the seals. Kits are cheap, and it isn't that much work to rebuild a caliper. Hope you put a good coat of silicone grease on everything.

 

[moribundman]

Yes, everything was lubed properly.

By the way, I could not find an internal pipe wrench that would have been big enough to fit the piston for extraction. Luckily, the "hydraulic method" worked fine and without the piston flying into the neighbor's yard.

 

[Audi Junkie]

I just did my rears. They were siezed. It took some doing to get the guide pins out and when I did there was a lot of rust. I reamed the bores out with sandpaper and a drill bit. I know it's primitive but I wanted to get it done and had no other tools so I did it as best as I could. On the front, I have a broken bleeder bolt. Instead of buying new (rebuilt) calipers, I have a new set off a B6, the same except with big ears. I can pull the units apart and swap the parts to get me a new set, excepting the mounting ears.

 

[labman]

Pack the caliper with rags and give the fluid inlet a shot of shop air. Chances are if that doesn't pop the piston out, it is shot and you may as well pick up a rebuilt caliper.

I have heard of people rigging up to pump grease into the caliper.