front caliper

seattle##gs · Apr 3, 2020

I am working on a front caliper which seems to have seized up long ago. Neither puck responds to compressed air. It is now soaking in penetrating oil. I would like to apply some heat so what temp can I safely use?

Bernhard · Apr 3, 2020

seattle##gs said:
I am working on a front caliper which seems to have seized up long ago. Neither puck responds to compressed air. It is now soaking in penetrating oil. I would like to apply some heat so what temp can I safely use?

Safest boiling hot water.

kommando · Apr 3, 2020

As the seals will need renewing 200C. I heated mine up with a propane torch after soaking in diesel so lots of funds but it worked.

marshg246 · Apr 3, 2020

seattle##gs said:
I am working on a front caliper which seems to have seized up long ago. Neither puck responds to compressed air. It is now soaking in penetrating oil. I would like to apply some heat so what temp can I safely use?

Look about 70% down here: https://www.gregmarsh.com/MC/Norton/Norton_1972.aspx

This always works for me. Yes, I'm a widower or I wouldn't dare use a good pot and the kitchen stove!

SEd27 · Apr 3, 2020

Though I have not done it personally, I’ve read that some have had good success with pumping the caliper full of grease. It seems to have a better hydraulic effect than air.

Bernhard · Apr 3, 2020

marshg246 said:
Look about 70% down here: https://www.gregmarsh.com/MC/Norton/Norton_1972.aspx

This always works for me. Yes, I'm a widower or I wouldn't dare use a good pot and the kitchen stove!

Novel way to cool a caliper piston, put a ice cube inside it.

dynodave · Apr 3, 2020

SEd27 said:
Though I have not done it personally, I’ve read that some have had good success with pumping the caliper full of grease. It seems to have a better hydraulic effect than air.

Pneumatic (compressed air) is outright dangerous.
Hydraulic is far superior. You can even use water instead of grease or oil. Only caveat is you ALWAYS run a #xx drill bit down the passage to the rear chamber to be sure it is not full of corrosive residue crud. You CAN break/split the caliper as it approached 2500psi...POW... (try that with your compressor air LOL) maybe 2000 psi from you oxygen cylinder and shoot it to the next state...
Want to see the split caliper?....

Torontonian · Apr 3, 2020

Order in new seals and stainless , not steel pistons. Heat, cold ice , wood and violence .

NORTSTER1974 · Apr 3, 2020

Since you are not going to re use the pistons, what I did with the last one that gave me major problems was soak it in Kroil. Then carefully drilled and tapped each piston. Obviously the outboard one first. Then I used the old trusty slide hammer to get them out. Pretty easy job. This was after all else failed, but why waste your time. Remember to remove the outer seal once you have removed that piston.

Scout63 · Apr 3, 2020

Do not use compressed air. I used it on the bottom piston, heard a pop and then heard the piston hit the other side of the garage after just missing my forehead. Lesson learned.

seattle##gs · Apr 3, 2020

I put a piece of 3/8 material between the pucks when I use air. I got the outboard piston out but the inboard is pushed all the way back in. Is it near impossible to get air or fluid behind it at that point? The first one was heavily corroded, I have two new stainless pucks and a rebuild kit. Boiled the caliper for an hour and used Kroil. There is a spray available online for freezing electrical components instantly. It would work better than ice cubes. Last one I got was from Radio Shack.

kommando · Apr 4, 2020

seattle##gs said:
Is it near impossible to get air or fluid behind it at that point?

Stick the released piston back in just enough so its just past the seal, put you piece of 3/8 material back in and then get a metal oil can and pressurise the caliper using your 3/8 material to only hold the previously released piston in place and the stuck one should start to move.

cliffa · Apr 4, 2020

I drilled through the side of the piston exposed by the recess for the pads tabs. Then with the caliper warm and brake fluid dribbled around the piston, used a rod to move it a few degrees either way. As soon as the seal released when it got some brake fluid around it it started to come out.

seattle##gs · Apr 4, 2020

mission accomplished. The bleed passageway was blocked with a clay-like crud. I used a small drill bit to clean it out and pour in some Kroil and let sit for an hour. It popped right out with some air. Then the long clean up began...

seattle##gs · Apr 4, 2020

By the way, my little compressor is probably 100 PSI at most...good for filling tires and blowing things off. Nowhere near 2000PSI. It still sounded like a gun going off.

cliffa · Apr 4, 2020

seattle##gs said:
mission accomplished. The bleed passageway was blocked with a clay-like crud. I used a small drill bit to clean it out and pour in some Kroil and let sit for an hour. It popped right out with some air. Then the long clean up began...

Mine was the same, but it looked like hardened jelly. I reckon it was emulsified brake fluid. Due to all the stories I'd heard about problems bleeding the brakes I ran a larger drill bit through all the passageways to clear them. It made me appreciate the value of changing the fluid regularly.

RoadScholar · Apr 4, 2020

The hydraulic method is the safest and best. You can use the the master cylinder, with the caliper dismounted and pads removed start pumping. The outer piston, usually, wants to come right out and must be restrained so that the inner piston feels all the pressure. You can do this with hose clamp and metal stock; the possibilities, however, are many. Once the outer piston is restrained the inner should come right out.

Once the caliper body is bare and clean inspect the seal grooves for oxidation; a Dremel with a wire brush works well to clean these grooves, but wear eye and face protection because these wire brushes don't last long and trow off their bristles with significant velocity.

Best.

Tornado · Apr 4, 2020

I guess I was fortunate when reviving my FC. I used the MC with whatever was still within the passages and the pistons came out OK. New seals and SS pistons went in after thorough cleaning. Bleed took many days to get right trying different methods. Ultimately in frustration I started rapid flipping of brake lever while watching fluid in reservoir. After maybe 50 flicks, I saw a few micro bubbles emerge from the tiniest hole at bottom of reservoir. Everything was firm after that.

seattle##gs · Apr 4, 2020

I have always been leery of using any kind of power tool in the bore of the caliper, afraid that it might remove aluminum. If you have cleaned the o-ring groove successfully with no leaks I will try that method. The piston fit the bore easily but it seemed there was a lot of resistance going through the 0-ring, more than I remembered. I used a C-clamp to push the piston slowly past the o-ring. It looked to me that the groove was completely clear but even a speck would increase the pressure.
Also, it would seem that the caliper would work differently in cold weather than full summer heat.

maylar · Apr 4, 2020

Dremmel also has a bristle wheel that's much less aggressive than the wire one. Eye protection still recommended.

front caliper

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