Originally Posted By: moribundman
Originally Posted By: labman
Right! I doubt how much good fluid flushes do the part of the piston inside the seal. They are totally useless as far as the part outside the seal goes, which is where the pistons rust.
"Where the piston rusts."
Here's the 11 year old piston of my left front brake. While aluminum surely can corrode, the only spot where I see some staining is away from the groove in the piston that holds the piston boot. There's not rust or corrosion on any part of the alu piston that is protected by the boot. Then again, I do flush the brake fluid every two years (as required by the car maker) and I do replace all piston seals and boots every 4 years.
So, you guys got rusty iron or steel pistons?
Like I say, you eventually need to replace the old, worn rubber parts in a caliper. I am sure most of the calipers I saw that had the pistons that were rusted never had any maintaince until they failed. I also think cold weather may be a factor in hardened seals letting in salt and moisture.
Originally Posted By: mechtech2
Not many of us are in the business of rebuilding calipers for sale - maybe years later.
Brake fluid is all we should therefore use when rebuilding them.
Brake fluid is hygroscopic, silicon grease isn't. If you are planning on keeping something for a while, best put the caliper back together with a silicone grease.
Originally Posted By: labman
Right! I doubt how much good fluid flushes do the part of the piston inside the seal. They are totally useless as far as the part outside the seal goes, which is where the pistons rust.
"Where the piston rusts."
Here's the 11 year old piston of my left front brake. While aluminum surely can corrode, the only spot where I see some staining is away from the groove in the piston that holds the piston boot. There's not rust or corrosion on any part of the alu piston that is protected by the boot. Then again, I do flush the brake fluid every two years (as required by the car maker) and I do replace all piston seals and boots every 4 years.
So, you guys got rusty iron or steel pistons?
Like I say, you eventually need to replace the old, worn rubber parts in a caliper. I am sure most of the calipers I saw that had the pistons that were rusted never had any maintaince until they failed. I also think cold weather may be a factor in hardened seals letting in salt and moisture.
Originally Posted By: mechtech2
Not many of us are in the business of rebuilding calipers for sale - maybe years later.
Brake fluid is all we should therefore use when rebuilding them.
Brake fluid is hygroscopic, silicon grease isn't. If you are planning on keeping something for a while, best put the caliper back together with a silicone grease.
