Was wondering if any one else has ran across this.

I was planning to replace my brake pads on the truck last weekend and when I got thing apart, I was bit shocked to see that one of the caliper pistons was rusted so bad that the cap a broken loose

As it turned out I had the work size pads (for under 8500 lbs not over). So I slipped the cap back on the piston and stuff things back together.

I was replacing the pads since I planning a 3000 mile trip at the end of the month to pick up a used (free) 5th wheel from my brother-in-law in Co

I don't know if the broken cap could have been issue on long drive just happen I found it and not big deal to replace

I bought manufactured calipers which are going in this weekend..

 

I don't get what a "cap" is on a caliper piston - explain that a little better

Oh, and WELCOME to FTE! - visit the NEW MEMBER thread at the top of the forum.

 

What is a cap, well I would have never thought I would need to explain what a cap is for the piston on the caliper. Since I assumed that the piston was a formed tub with the "cap", instead its a round tube with a separate metal cap

This round tube (the caliper piston) has the cap (end that presses against the brake pad) pressed onto it. In my case the truck was clearly exposed to a lot of water and the "cap" rusted off the reset of the body of the piston (the tube part).

I will take pictures this weekend and post them

 

Is it a shim?

 

No not a shim much more of a cap that appears to be pressed onto the piston. At on time the truck must have set in water up to the caliper and water got inside the piston -- which rusted through and the "cap" came loose..

Remove the "cap" and you see the hollow tub (front part) of the piston

 

Couple picture links of the piston

 

Those are plastic pistons. They are broken just replace the caliper. Boots are ripped anyway, its just a matter of time now.
I dont know why you have a metal cap on plastic pistons as I dont on my truck which could have a greater braking load placed on it.

 

I do not think that the pistons were plastic - they appeared to be original equipment.

Any way could not swear that they were not plastic -- did not check and I already took them back for core charge

 

I've never seen a plastic brake piston before or one that was corroded that bad. I'm pretty sure that those are metal otherwise they wouldn't have rusted like that. I've seen the caps come off before but not rust the entire ring off. Looks like it probably got some salt/water in the piston during some winter months and it just ate it up.

 

My '94 f350 has plastic pistons stock, but without the metal cap. Plastic brake pistons for a '97 f250: While we find your parts, please enter your ZIP Code at PartsAmerica.com

 

Wow. That disturbs me a little. Never would have thought it would be plastic (or phenolic which is a little different).