Stuck brake piston in calliper - how to remove

[eil]

Will try pushing it back in a bit first as have no access to compressed air bar a diving cylinder at 230bar

Don't take us too literally when we say "compressed air." I have only ever used a leaky $10 bicycle tire pump for this task. You don't need hardly any volume, just pressure.

As for the messiness of this method, just drain the brake fluid out and wrap the caliper in a towel then pump away. Couldn't be easier.

he front calipers are easy because there is only the one piston in each, but the outer piston of the rear caliper tends to come out first, leaving the inner one still inside that part of the caliper. You have to "restrain" the outer piston slightly with a piece of wood or a "C" clamp, so that the two pistons move by approximately equal amounts until they are both nearly completely out. Then you separate the two caliper halves, and the pistons can easily be removed by hand.

That's one way, another is to block off the pass-through port by sandwiching a piece of rubber between the two halves and bolt them back together. Once they're isolated from each other, just pump each piston out separately.

[ukjules]

caliper out using a pump

Ill try the bicylce pump method !
But how on earth do you get a good seal on the inlet to the callipers ?

I can put back together but there is a reason why they are off, it is an old
bike and evrything is knackered, hoses, everything.
Ill have to rig soming up until i get new hoses etc.

the bottom line is I have moved them (piston/cylinder) in and they went in easily.
I only need to get them out now.
Ill try a bicycle pump ......

Cheers for advice

[chuck hahn]

I use the air method..and still sometimes they wont move even at 90 PSI on the hose. At that point i use a torch and heat the piston till I see the oil at the edges of the seal start to bubble ( boil ) a little. Then just a quick hit with the air and they are out. I always replace the seals so I personally dont care if they get a little soft from the heat.

[ukjules]

I know I am going to have to connect up the hoses (Remeber they are knackered so I will
have to buy new ones now rather than later) but I am trying every other option.

Air foot pump:
As below - I just about managed to rig something up and get 80lbs press on a foot pump for a time.
Nothing moved (Remeber I have managed to move them in)
I am yet to be able to heat up the pistones - will buy a torch and report.

I think I am going to have to go to a garage and ask if i can use there air line.
You know garages though - they never like that.

Foot pump method 1.jpg

[chuck hahn]

Keep your finger out from between the caliper and the piston. I have put one of the old pads against the caliper body opposite the face of the piston to catch it when she lets loose. She will come out with considerable force and make a pretty loud pop.

[megatwin]

I always use the master cylinder to pump them out,as said above,but would add that if you have a multi piston caliper,I always use a block of wood,
or something to block full travel of the caliper piston.
If you don't,one piston will pop all the way out,and leave the other one still stuck in the bore.
Usually,when they are close to the end of the caliper,it's very easy to go ahead and pull them out the rest of the way,no need to blow them all the way out,and less mess,too.

[ukjules]

I tried the following - but it is yet to shift them:

Heated up pistons in the callipers with a blowtorch
Retried the foot pump method to almost 80 - 90lb's according to footpump.

I am trying not to use a garage but it seems I will have to
use one of a garage air lines.

I will also try and get some more brake lines (old ones perished) to use the
mater cylinder in situ method.

Will advise

[Crankthat]

Air line attached to bleed nipple?
Bleed nipple opened (backed off) enough that air is getting through to fluid chamber?

Other then that I am out of ideas.

[chef1366]

Use penetrating oil and not WD
Use an o-ring between the air and port.
As Chuck said use heat but I would boil some PJ1 Blaster in there too. WD does not penetrate.

[chuck hahn]

I do shoot them with some PB Blaster first and try the air like you said Bill. But then the heats the last stand and youll see the oil start to bubble a little.

And to the guys that use the master cylinder to pump it out. Yup..works a champ for single pot front calipers. But with twin pot fronts or the rear stockers which have two pots, when whichever one comes out first your done with the other still stuck. This when you will need the air / oil /grease guns trick in the tool bag.

[JTGS850GL]

I do shoot them with some PB Blaster first and try the air like you said Bill. But then the heats the last stand and youll see the oil start to bubble a little.

And to the guys that use the master cylinder to pump it out. Yup..works a champ for single pot front calipers. But with twin pot fronts or the rear stockers which have two pots, when whichever one comes out first your done with the other still stuck. This when you will need the air / oil /grease guns trick in the tool bag.

Chuck,

On twin pot calipers I use two small C-clamps I clamp one down to hold the piston in and use one clamp a little loose to free that one up. Once one moves out you can loosen the other clamp to get that one to break loose as well. Usually once they begin to move it's a simple process to twist them out. It's worked for me.

[chuck hahn]

Never thought of that...another trick for me to store to use. thanks.

[megatwin]

I do shoot them with some PB Blaster first and try the air like you said Bill. But then the heats the last stand and youll see the oil start to bubble a little.

And to the guys that use the master cylinder to pump it out. Yup..works a champ for single pot front calipers. But with twin pot fronts or the rear stockers which have two pots, when whichever one comes out first your done with the other still stuck. This when you will need the air / oil /grease guns trick in the tool bag.

That's why I stated in post 21 to use a block of wood to keep them from popping all the way out.
JTGS850L using the c-clamps works well also.

[chuck hahn]

Did not see the post!! Bet the old pads would work also.

[ukjules]

Many thanks for info - all good advice.
I was and only have used WD40. Thats probably why in my life I use a impact driver so much.

PB - of course is only in the USA.

i will try "plus gas" as internet say this can work ?