I disassembled my calipers to be sand blasted and painted. Any tips and suggestions on how to mask off the big caliper piston hole ? Need to do some sand blasting around it. Also the top of the caliper piston is rusty and the inside exposed to the weather side of the caliper piston is rusty, can I sand blast that?
Caliper Masking off and sandblasting
- Thread starter Rust_Belt_Pete
- Start date
Put the old piston in there, get new ones for rebuilding unless the chrome is perfect.
looks fine. I was worried from seeing the caliper bore.
insert the piston and go to town on sand blasting the exterior.
insert the piston and go to town on sand blasting the exterior.
When I did mine I masked the inside of the bore and then shoved a load of newspaper in there.
My pistons were scored so I decided to replace them. Wrapped electrical tape around telhe top of pistons and jammed them in. Did a good job.
Blast the whole thing! It's not an engine...the bore is not the sealing surface. It shouldn't even ever touch the piston. I have a caliper rebuilding business.....We do mainly air cooled porsche and vintage british. All of our iron castings go through an automatic shot blaster, we blast everything. It's the way it's been done since the beginning. Aluminum calipers with anodized bores...absolutely protect the bores and threaded holes at the very least to protect the anodizing while blasting...or simply forgo the blasting and do minor sanding before refinishing (if painted).
The piston in your picture looks like it was either not even wiped down and it has fluid and hair and crud stuck to it, or it's garbage. Piston should look relatively flawless, of you'll have problems.
The failure mode of just about every cast iron caliper that's come through the shop has been rust between in the bore between the boot and the seal. About the only reason I wouldn't blast the bore is if there WAS NOT rust in the bore between the boot and the seal, and there was still factory plating in place on that surface....then I'd lightly clean it with some mild scotchbrite such as not to go through the plating, and blast everything else. Most OE calipers these days don't have any plating in the bores though, so make sure you use a proper assembly lube that contains rust inhibitors (don't use brake fluid), and then get one of those little curved tip syringes they have to feed medicine to cats and fill it with silicone dielectric grease and squirt the bellows of the boots full of grease before you put it back together....if that "dry" area between the seal and boot is full of grease, it can't get full of water or dirt or anything else and caliper life will be greatly increased.
Clean the grease outta the slide pin holes in the bracket before you blast it....
The piston in your picture looks like it was either not even wiped down and it has fluid and hair and crud stuck to it, or it's garbage. Piston should look relatively flawless, of you'll have problems.
The failure mode of just about every cast iron caliper that's come through the shop has been rust between in the bore between the boot and the seal. About the only reason I wouldn't blast the bore is if there WAS NOT rust in the bore between the boot and the seal, and there was still factory plating in place on that surface....then I'd lightly clean it with some mild scotchbrite such as not to go through the plating, and blast everything else. Most OE calipers these days don't have any plating in the bores though, so make sure you use a proper assembly lube that contains rust inhibitors (don't use brake fluid), and then get one of those little curved tip syringes they have to feed medicine to cats and fill it with silicone dielectric grease and squirt the bellows of the boots full of grease before you put it back together....if that "dry" area between the seal and boot is full of grease, it can't get full of water or dirt or anything else and caliper life will be greatly increased.
Clean the grease outta the slide pin holes in the bracket before you blast it....
I used a chemical derust- worked very well.
I would make sure the bore and the seal groove are cleaned, smooth and rust free to ensure proper operation and a good seal. After that you can worry how pretty it will look like on the outside.
And looking at the picture, the piston seal as well as the boot grooves need to be properly cleaned up.
And looking at the picture, the piston seal as well as the boot grooves need to be properly cleaned up.
Any suggestions on tools for that. Trying to make the area where the piston dust boot flat and even so it seals well.
I’ve always improvised and made my own. I had good luck with a small flat head screw driver or a pick just scraping the bigger bits off. Then I would put 120 grit sandpaper over the head and start going around the groove.
The biggest challenge are the corners and for that I would use a pick. I would go around the circumference to see if it catches on anything. Then focus on those areas.
You won’t get the surface to look like freshly machined one, but that’s not the goal. The goal is to have a smooth surface for the seal and dust boot to seal against.
I didnt even think of doing that, thank you. Yeah thats how most moisture makes its way in to the caliper and the piston. Pack it with silicone grease since it doesn't care about heat any way.
