CNC 603 rebuild

[Purple Frog]

Sportsfans,

I'm at wits end. (it was a short trip, i know...)

I have four CNC 603 aluminum billet 4 piston calipers.
They were rebuilt by a reputable racer a few years ago. Then put in a box.

I can not get them to function. The pistons seem frozen in place. Some don't want to bleed.
I have used the master cylinder for pressure as well as 120 psi of air pressure.

At this point I'm ready to investigate sending them to a rebuilding service. But, once you look that up on the interweb there are thousands of options.

I trust the recommendations of folks on this site.

Any idea where to send them?

[Purple Frog]

Might have found my own answer.
CNC says they will rebuild them for $40 each plus parts.
Plus shipping back and forth across the U.S. of A.

[Brian]

while your answer is best, I was going to say that a grease gun can develop 10,000 psi of pressure, in an extremely controllable manner. I've used a grease gun with Marvel Mystery oil to free up stuff before.

[HayesCages]

I use a torch and apply just enough heat to get the seals to melt a little. $40 is pretty reasonable though.

[bear01011]

If it helps you any, I have an entire lot of CNC seals for sale:

http://www.apexspeed.com/forums/showthread.php?t=76702

[DaveW]

The seals have obviously either swelled or bonded themselves to the piston.

I would suggest

(1) fill the pistons with ice and heat the calipers (350F or so with a propane torch) to see if that amount of differential expansion will loosen the seals' grip and apply air pressure, etc., to try to move them.

(2) If that doesn't help, use dry ice to shrink the aluminum, compressing the seals, then while still cold try air pressure, etc. to try to move the pistons while the seals' coefficient of friction is reduced by the cold.

(3) If that still doesn't work, repeat # 1.

If no success, then send them back for a rebuild.

[romoman]

For $40 plus shipping, there is not question on the right answer.

[Purple Frog]

My problem is that I'm the King o' Cheap. $200 is a fair price to have $2,200 worth of calipers. I'm afraid that once the calipers are in California they will say they new new pistons, new bleeders, etc. etc. and a $200 bill will jump to $400, for something i should be able to do myself. Plus the person that rebuilt them and put them in the box is somebody i trust, so I'm hoping it will just be a case of freeing them up.

I'm going to continue the struggle all weekend, trying DaveW's ideas, if no solution by Monday, off they go to California.

[SteveG]

Caliper piston "wrench"

I used one of these to free up and disassemble some old, ratty, stuck LD20s with low effort and no apparent damage.

Steve

[DaveW]

Only disadvantage would be that if the pistons are fully submerged, there's no way to grab them.

[HayesCages]

Measure ID of pistons, turn round that's .010" smaller and about the same length as piston is deep, drill hole in center of flat end, tap hole to whatever size is appropriate, cut round in half down center of hole - make cut about .040 wide, insert halves in piston, screw in bolt that fits your slide hammer, pop pistons out.

[DaveW]

Measure ID of pistons, turn round that's 010" smaller and about the same length as piston is deep, drill hole in center of flat end, tap hole to whatever size is appropriate, cut round in half down center of hole - make cut about .040 wide, insert halves in piston, screw in bolt that fits your slide hammer, pop pistons out.

Brilliant!

[Roland V. Johnson]

CNC is a couple of blocks away. Chuck, the owner is a real straight up guy, and very proud of the things he has made.

[Purple Frog]

Roland, that is the kind of info I appreciate. Thanks!

All the work HayesCages is laying out, while brillant, is beyond my shop's capabilities and harder for me to do than lay out the $200.

OBTW, the pistons are flush with the inside edge of the caliper.

[Rick Kirchner]

you guys missed the obvious:

Froggie - what are you building.........

[Purple Frog]

I am rigging up a single master cylinder on a pedal with 7' of steel braided -4 line.
Mrs Frog can push the pedal and I wll hold the problem calipers on the shop floor.
I'm thinking I can get a lot more than 120 psi out of that arrangement.

Problem is if one piston moves, how to trap it until others move.

$40 is starting to look like a deal. LOL

[HayesCages]

Klamp it Jed.

[Purple Frog]

I'm glad they are only 4 piston calipers... I only have 3 clamps that are the correct size.

We have worn shorts all season until this evening, then you let "weather" escape from Idaho into our neighborhood.

[Roux]

I back up Brian on this one. Brazed a few fittings together and used a grease gun. Works every time

[J Leonard]

Hard pipe direct, don't use a grease zerk or whip hose. Just leave the grease in, your going to clean it all up anyway.

[Fred Michael]

I am rigging up a single master cylinder on a pedal with 7' of steel braided -4 line.
Mrs Frog can push the pedal and I wll hold the problem calipers on the shop floor.
I'm thinking I can get a lot more than 120 psi out of that arrangement.

Problem is if one piston moves, how to trap it until others move.

$40 is starting to look like a deal. LOL

Put a piece of wood or plastic in place of where the rotor would be, thick enough that the pistons can't come all the way out of the bores. When the pistons release they will hit the wood and not damage the pistons

[Purple Frog]

Success!!

I had a text from Eric Langbein telling me that brake line pressures can be pretty high. Higher than 120lb. not to panic.

And I knew these calipers had been rebuilt by a person I trust a lot.

So... I rigged up a -4 line from a clutch master cylinder in a car in the shop out to the floor. Then by bleeding the cylinders and pumping the pedal i could 'creep' the pistons out basically one at a time. As one would start moving out i would put a clamp on it, then pump the pedal again. etc. etc.

Was a big messy. But i got all 16 pistons out. Inspected. Put rubber grease on them and reinstalled. No heat. No ice. But about a pint of brake fluid used up.

Thanks again to Apexspeed. Great input got me thinking.

And now i own a complete set of replacement "O" rings. Thanks Kim Baker.

[DaveW]

Super. Glad that worked.