The owner of the silver SI 330GT told me he was losing brake fluid, so when I found a puddle of brake fluid below the left rear wheel, I at least had a place to start looking for a leak. I found some pretty crusty brake caliper pistons, and this one looked like it had seized and jammed.

Upon removing the piston, I found a gummed up mess. These brakes have not seen regular brake bleeds, and water had gotten into the system causing the fluid to fail and rust out the calipers. My concerns were if this was happening on this piston, the others were going to look the same.

After removing the old fluid and gunk, it wasn’t looking like these pistons were simply going to need new seals.

Bead blasting got the piston looking pretty good on the outside.

The insides, however, showed how the water had rusted and pitted the cast iron bores of the bores.

After I spoke to the owner, we decided to take all the brake calipers apart to see what else was wrong. The front calipers weren’t in any better shape, but these calipers had been previously sleeved in brass. I prefer sleeving these calipers in stainless steel, but brass sleeves are another option. I had my calipers sleeved in brass over 20 years ago, and they’re holding up fine, but I have found stainless more durable, When pistons don’t see regular fluid changes, brass can show corrosion, and form ridges that then need to sanded smooth changing the bore dimensions.

The front calipers cleaned up fine, and I was able to install new seal kits, but the rear pistons were sent out to my brake rebuilder for new stainless steel sleeves.