Attempting to blow pistons out of brake caliper - what nozzle for air gun?

[BrakeL8]

Perhaps a very stupid question here- but I'm wondering how others are using an air compressor to do this? Do I need to get one of the guns w/ the tapered rubber tip (like attached image) and then just hold this pressed onto the brake line connection point w/ the bleeder screw obviously still shut?

My gun has a tip that's too small to make a seal on the caliper, I've read a lot of threads here yet don't see this part mentioned so want to make sure I don't need to figure out the threading (3/16"?) and create some screwed in adapter thing in order to do this successfully.

Thanks

[jamesjedi]

Use a cheaper version. The tip can be bought at any discount parts store, or just get a different air nozzle.

Make sure you use wood or rags between the caliper and piston. It comes out with enough force to damage the piston and hurt your hand. It comes out as a projectile.

Do not be surprised if it does not come out if you calipers have sat on a shelf for a few years. If used recently they should come out.

[Cajundaddy]

Air is compressible and can be a problem, launching your pistons into the wall across your shop, or worse. Brake fluid makes for a much gentler, yet somewhat messier piston release. Remove the calipers, leave the hydraulic line connected, place the caliper in a catch bucket, and one or two pumps on the pedal will pop the pistons gently into your waiting bucket.

[BrakeL8]

Originally Posted by jamesjedi

Use a cheaper version. The tip can be bought at any discount parts store, or just get a different air nozzle.

Make sure you use wood or rags between the caliper and piston. It comes out with enough force to damage the piston and hurt your hand. It comes out as a projectile.

Do not be surprised if it does not come out if you calipers have sat on a shelf for a few years. If used recently they should come out.

Yeah they're working brakes, just need to change out seals as they're slightly torn (found during pads/rotors) and figure I should give everything a good clean and inspect all pistons while i'm in there. I've heard the bit about the projectile- just wasn't sure how to connect the air. Ty

[juanbenae]

a rubber tipped nozzle like you show, or even the less expensive, simpler non pistol type will work. I usually put a piece of 1x or slimmer wood between the pistons to keep them from clashing together when one breaks free and out.


usually only one will come out with air applied so the 1st one that starts to dislodge I C clamp it, reapply air to get the second one moving. it sux getting one all the way out then trying to get the second one to dislodge with the other side open.




sounds like a bottle of champagne being cracked open when they come out...

[yundar]

I have used just a standard rubber tip air nozzle pressed by hand into the caliper. For really old or stuck brakes you may have to go with hydraulic pressure. If the caliper is already off the car you can find a zerk fitting that threads into the brake line port. Use a grease gun to pressurize the caliper and the pistons will come out. You need to use a c clamp to limit travel on the pistons as one piston will tend to break loose before the other. Don’t let that piston come all the way out before the other one or you will lose pressure and still have one stuck piston. You kind of have to work each piston out a little at a time swapping back and forth so they come out at the same rate.

[Superman]

I like to remove the pads, then use a thin piece of wood (like two of those very small paint stirring sticks) between the piston and rotor. This gets the pistons out, using the brake pedal. However, the purpose of the sticks is to prevent the pistons from actually coming out of the bore. The goal is to get the pistons out as far as possible without actually coming out of the bore. In this way, the pistons can then be removed, on the bench, with just a little gentle coaxing with pliers, being careful not to touch the business surface of the piston(s).

[James Brown]

^^^^ perfect^^^^

[djdsc]

Use a pump grease gun. Surprisingly, unscrew the zerk nozzle and see if the threaded hose fitting won't screw directly into the bleeder threads. Mine does. Compressed air is like launching a missile.

[safe]

Originally Posted by BrakeL8

Yeah they're working brakes, just need to change out seals as they're slightly torn (found during pads/rotors) and figure I should give everything a good clean and inspect all pistons while i'm in there. I've heard the bit about the projectile- just wasn't sure how to connect the air. Ty

Then just leave the pistons alone and replace the dust boots. I could also argue that the dust boots are relatively pointless to begin with, specially in California...

But if you must, do as Cajundaddy says, much cleaner, easier, less dangerous and should they be stuck, very powerful.
If the pistons are fine you should be able to pull them out with pliers.

[Bob Ashlock]

the grease gun is the way to go. Messy, but safe and guaranteed results.

QUOTE=djdsc;10426776]Use a pump grease gun. Surprisingly, unscrew the zerk nozzle and see if the threaded hose fitting won't screw directly into the bleeder threads. Mine does. Compressed air is like launching a missile.[/QUOTE]

[brighton911]

Similar to Superman, I use decreasing thicknesses of pieces of wood between the pistons to prevent them from blasting out of the caliper. And unless the pistons are seized, I just use a rag in the inlet port to semi seal the air nozzle. Works fine and prevents brake fluid spray in your face. Anyone else hate the feel of brake fluid on their hands?

[kuba_kuba]

Originally Posted by bob ashlock

the grease gun is the way to go. Messy, but safe and guaranteed results.

Quote=djdsc;10426776]use a pump grease gun. Surprisingly, unscrew the zerk nozzle and see if the threaded hose fitting won't screw directly into the bleeder threads. Mine does. Compressed air is like launching a missile.

[/quote]

+1

[trond]

use the brake pedal and brake fluid if possible. If you use a grease gun you will need to split the caliper to get all grease out, with the possible consequences to stripping those riebe bolt heads especially... better to avoid that

[pgeorgeson]

I just wrapped the tip of my air gun with electrical tape. Worked fine. (Also with something in the capiler so they didn’t blow out too hard. I used the wooden handle of my hammer)

[juanbenae]

#76! how was your weekend at thill? saw a couple photos of your car in the background of paddock shots posted on the PRC FB page. you still in the spec class or have you moved to GTU as well? hope you guys are all doing good! I miss the paddock as much as the racing.

[GH85Carrera]

I looked a the process, and even after I rebuilt them, they were still going to look old and ugly. I choked up the cash to send them to PBM and they came back looking like new.

I was thrilled with the final results.

[Bill Douglas]

time for safety glasses and overalls/coveralls.

When I did mine, wooooo, brake fluid all over the place including the ceiling.

[grant lyon]

Alternative: after pulling calipers off car, I used my road bike pump with presta fitting held over/on the short hardline flare end. With a wooden block clamped with offset to one side, then the other between the pistons to walk the pistons out gradually. Not as professional or impressive as air compressor, but that was the point since it was easy to control pressure applied. Rags over/under caliper to catch brake fluid/projectiles.

[BrakeL8]

Originally Posted by grant lyon

Alternative: after pulling calipers off car, I used my road bike pump with presta fitting held over/on the short hardline flare end. With a wooden block clamped with offset to one side, then the other between the pistons to walk the pistons out gradually. Not as professional or impressive as air compressor, but that was the point since it was easy to control pressure applied. Rags over/under caliper to catch brake fluid/projectiles.

ah that's clever. didn't think about using my bike pump.