No pressure in front caliper after draining

[Falco]

Thought I'd overhaul the front brake caliper over my long weekend, but it's all gone a bit wrong.

Removed the pads and started pumping out the pistons (2 pot caliper), held one in a bit so they wouldn't come out at the same time and I could seperate them. However I overdid it and when the front came out, the rear was still firmly in. Thought I'd just slip the front one back in, reconnect and fill it up and pump them out again, but I can't seem to get any pressure to build up.

I assume its an airlock but I can't seem to get rid of it. I've tried bleeding the usual way, I've tried reverse bleeding it (just comes out around where the tubing meets the bleed nipple), Ive tried using the syringe to suck brake fluid through (got some bubbles and then just fluid), tried putting the end of the tubing in some fluid and then just pumping the lever (fluid goes through but the lever won't harden at all).

I don't need it to be perfect at this point, I just need the pressure to pump the pistons out, what am I missing? Why won't it build up any pressure?

[Rogerborg]

[Falco]

[Commuter_Tim]

[Falco]

Looks like the brakes aren't done with me quite yet....

Rebuilt the calipers and put it back on the bike with fresh pads, bled it, but now the front wheel is binding. It spins freely with the pads pushed back but once pumped out it starts to bind.

It's like the pistons aren't retracting properly, but all the sliding pins are greased and the pistons shiny clean. Whatever the issue is, the upshot is that the wheel is spinning maybe 3/4 of a rotation before stopping.

What's the next step in figuring this latest problem out?

[Kickstart]

Hi

Did you clean out any corrosion in the grooves the seals live in ?

All the best

Katy
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[chris-red]

I've yet to find a better way of bleeding brakes than, attaching a tube to the open nipple putting it in a jar of fluid and pumping the brakes till air stops coming out. It's simple, quick and for me, full proof.
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[Falco]

[kramdra]

Foot pump is ideal way to get pistons out, connect by bleed nipple.
Rubber sheet pressed with hand, will seal a vacant pot.
Use a scrap banjo, blocked up to seal that hole.

Care needed to avoid shooting piston into face or hole in celling.

[Falco]

Well I am at a loss now. double checked the the sliding pins could move well, that pistons are pumping out, tried it with less fluid in reservoir, with more in reservoir, pushing pistons back in with reservoir lid off to make sure there isn't too much fluid. I have no idea what could be the problem

Took it for a quick 1.5m ride, disc rotor was warm at the end but with no front braking whatsoever so its still binding.

Next up is to disassemble it again, but since it has already been cleaned and greased I am not sure I see what good it would do.

[Kickstart]

Hi

Nothing majorly obvious then (assuming the calipers are not bent). But if sliding calipers the pins aren't overly lubed (ie, could seal the pins enough so they can push slightly).

Other chance (but not common), are the seals directional ones?

All the best

Katy
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Falco]

[Kickstart]