Big Blue's Transformation

[Gary Lewis]

You may have this, but just in case, I have a 3-legged chuck-able wheel cylinder bore hone for when it comes to rebuild the calipers.

Lunch time, I take it. Just left the Mac's/Daylight lot (they were out ) and saw you go by.

Anyway, I shouldn't have to hone the calipers, should I? Doesn't the piston pretty much float in the bore and the seal takes the place of the rings?

The one caliper I've taken apart had a bit of wear on one piston, the one with the messed-up head, but the other one looked fine on the sides. Guess I need to pull the other caliper apart today while the twins are in Jenks and see what I have.......

[ArdWrknTrk]

Lunch time, I take it. Just left the Mac's/Daylight lot (they were out ) and saw you go by.

Anyway, I shouldn't have to hone the calipers, should I? Doesn't the piston pretty much float in the bore and the seal takes the place of the rings?

The one caliper I've taken apart had a bit of wear on one piston, the one with the messed-up head, but the other one looked fine on the sides. Guess I need to pull the other caliper apart today while the twins are in Jenks and see what I have.......

I can't see phenolic wearing steel.

Usually the fluid takes on water and when I falls out of solution it pits the bottom of the bores.

[Gary Lewis]

I can't see phenolic wearing steel.

Usually the fluid takes on water and when I falls out of solution it pits the bottom of the bores.

The bores on these calipers have no pitting. None. Here's a shot of what they look like, all the way around. And that's just surface rust - which you don't see with the naked eye. So I think they are in excellent shape and won't need the hone. Thanks anyway, Steve.

And, for those who want to know what's inside of a caliper, not much. Here's the total for two of them. And what I think needs to be replaced is: the seals, which are the square-cut o-rings on the corners; the piston boots, which are the seal looking things in the middle left and right; the bleed screws, which have cleaned up in blasting but which will rust quickly with no plating; and the pistons. The slide pins and their boots, which are across the bottom above the pistons, are ok. Not perfect as the boots were placed in a rusty bore and there are marks on them to match the rust. But, they are solid and I've removed the rust down to shiny metal.

And, speaking of that, the left caliper was in the blast cabinet about 30 minutes. Turns out the rust is tenacious and it'll take another 30 minutes to make it ready for powder - if I were to do that. But I'm not sure I want to start that for this project. Thoughts?

 

[ArdWrknTrk]

The bores on these calipers have no pitting. None. Here's a shot of what they look like, all the way around. And that's just surface rust - which you don't see with the naked eye. So I think they are in excellent shape and won't need the hone. Thanks anyway, Steve.

And, for those who want to know what's inside of a caliper, not much. Here's the total for two of them. And what I think needs to be replaced is: the seals, which are the square-cut o-rings on the corners; the piston boots, which are the seal looking things in the middle left and right; the bleed screws, which have cleaned up in blasting but which will rust quickly with no plating; and the pistons. The slide pins and their boots, which are across the bottom above the pistons, are ok. Not perfect as the boots were placed in a rusty bore and there are marks on them to match the rust. But, they are solid and I've removed the rust down to shiny metal.

And, speaking of that, the left caliper was in the blast cabinet about 30 minutes. Turns out the rust is tenacious and it'll take another 30 minutes to make it ready for powder - if I were to do that. But I'm not sure I want to start that for this project. Thoughts?

I think the piston seals probably have a slight taper to their cross section.

If it were me (and I didn't want to powder coat them bright red) I would probably leave the surface rust and treat them to some passivation process like parkerizing or black phosphate coating.

Then at least they have a fighting chance.

I'm still amazed how rust free a 24 year old truck is down there.

[Gary Lewis]

I think the piston seals probably have a slight taper to their cross section.

If it were me (and I didn't want to powder coat them bright red) I would probably leave the surface rust and treat them to some passivation process like parkerizing or black phosphate coating.

Then at least they have a fighting chance.

I'm still amazed how rust free a 24 year old truck is down there.

Looks like the total for parts to rebuild the calipers is $31.29.

As for coating the calipers, if I don't PC them I could put a phosphate coating on them. But, I could also paint them with POR15 which would stick tightly to the rust. And, since the calipers don't get much UV the POR wouldn't really need a top coat. However, since I've learned that it is easy to rattle can the top coat while the POR is sticky, that's not a big deal.

Bright red!?!?

EDIT: I'll check for the taper.

[ArdWrknTrk]

Looks like the total for parts to rebuild the calipers is $31.29.

As for coating the calipers, if I don't PC them I could put a phosphate coating on them. But, I could also paint them with POR15 which would stick tightly to the rust. And, since the calipers don't get much UV the POR wouldn't really need a top coat. However, since I've learned that it is easy to rattle can the top coat while the POR is sticky, that's not a big deal.

Bright red!?!?

EDIT: I'll check for the taper.

So with $37 in pads you're in it for $68.29 and your time.

That's cool.

I hadn't thought of Paint Over Rust 15.

Can't say I've used it.

Generally I try to stay away from film forming coatings on the undercarriage.

But you seem to like it, and I trust your judgment.

I'll stop taunting you about the accent colors on BB.

[ArdWrknTrk]

So with $37 in pads you're in it for $68.29 and your time.

That's cool.

I hadn't thought of Paint Over Rust 15.

Can't say I've used it.

Generally I try to stay away from film forming coatings on the undercarriage.

But you seem to like it, and I trust your judgment.

I'll stop taunting you about the accent colors on BB.

Maybe that's just the way seals were long, long ago.

I imagine a manufacturer could accomplish the same by cutting a groove with an out of level floor.

Anyway the idea is for the seal to have bias and some stiction that causes the rubber to pull the piston back, but still allow it to advance as the pads wear.

[Gary Lewis]

So with $37 in pads you're in it for $68.29 and your time.

That's cool.

I hadn't thought of Paint Over Rust 15.

Can't say I've used it.

Generally I try to stay away from film forming coatings on the undercarriage.

But you seem to like it, and I trust your judgment.

I'll stop taunting you about the accent colors on BB.

Yes, it is cool. Thanks for the suggestion of rebuilding them.

As for the POR15, if the surface is properly prepared you won't get it off. But "properly prepared" is laborious for frames and the like as it requires serious cleaning and if the metal isn't rusty it requires a phosphate coating or media blasting to give it tooth.

However, I may well paint Big Blue's frame with it where I do the repairs. Someone has already painted the frame gray, and I have gray POR, so.....

And, I do expect to do some powder coating or POR'ing of other parts as I don't think the Sky parts come coated. But, I will order the panhard rod already PC'd as I don't want to have to remove the bushings to do that. Fortunately it comes in black.

[Gary Lewis]

Maybe that's just the way seals were long, long ago.

I imagine a manufacturer could accomplish the same by cutting a groove with an out of level floor.

Anyway the idea is for the seal to have bias and some stiction that causes the rubber to pull the piston back, but still allow it to advance as the pads wear.

Not everyone knows how that seal/o-ring works - although obviously you do. I think it is cool that it twists and then pulls the piston back, up to a point. Then the piston slips a little bit and the o-ring grips it again and twists.

That is, until the o-ring gets stiff or it gets damaged, like by a rusty piston. Which is one of the reasons why the phenolic pistons are a good idea - they don't rust.

[ArdWrknTrk]

Not everyone knows how that seal/o-ring works - although obviously you do. I think it is cool that it twists and then pulls the piston back, up to a point. Then the piston slips a little bit and the o-ring grips it again and twists.

That is, until the o-ring gets stiff or it gets damaged, like by a rusty piston. Which is one of the reasons why the phenolic pistons are a good idea - they don't rust.

They don't rust AND they're much less conductive than most metals.

So they don't transfer much heat from the pads to the fluid behind them.