Brake piston removal (after someone has bodged it)?

[julianf]

Ive got a caliper here, that some fool has tried to get working using a blow torch.

The result being that the piston is not just seized, but also the seal has melted and is bulging out where the rubber has melted and needed to seep.

Im wondering if there is some chemical that will seep and eat the rubber (i suspect not) or if it might be an idea to pressurise the unit with air, and then re-heat using a blow torch.

The issue here is that the unit is split, and i cant see how i can seal the halves in a non melting way.

Or maybe i could drill the base of the piston an use the hole for purchase of some sort of puller?

Really, some horrible chemical seems the simplest, but i cant see it being quick.

Any ideas?

 

[Ashley Burton]

Compressed air or could try this method:

 

[DaveB]

Unless it is unavailable, get a new or rebuilt caliper and let someone else worry about your seized one.

Don't use compressed air to eject the piston, use water or oil in an appropriate pump.
It is safer and you can apply far more pressure.

 

[Justme]

Dont use air. To risky.

 

[Ashley Burton]

Dont use air. To risky.

Not if you put a restriction in the caliper to stop the piston flying out at high pressure.

 

[Justme]

Not if you put a restriction in the caliper to stop the piston flying out at high pressure.

Still risky when the seals can blow, piston can split etc.

 

[rtbcomp]

Dichloromethane will soften rubber.

 

[RonA]

Once had to remove a seized piston on a lotus Elan front calliper. Basically used the technique shown in the video but only after applying 50/50 mix of paraffin & diesel to the piston for an hour or two. Even then the piston only moved a minute distance. Piston had to be forced back with a G clamp & the procedure repeated numerous times till the piston finally came free. New pistons & seals were then freely available, I’ve read they’re much harder to come by & most manafacturers are much keener for you to buy s brand new calliper.
RonA

 

[123hotchef]

I used air on mine when I rebuilt them

 

[Windy Miller]

I used compressed air to free a stuck piston once. As soon as I applied the air it shot out and clocked me in the eye. Obviously not quite as stuck as I had thought! Be careful...

 

[jerrytug]

Hi take care, squashed air is potentially lethal when (if) it eventually moves !
Big bang, dent in the bulkhead
Lateral thinking, or desperate last resort if its a very rare caliper..
if the previous attempt partly melted the seals, get a flame on it again and finish melting the pesky rubber?

Personally I might consider an exchange caliper. ( if available of course..)

 

[8ob]

I normally free them while still connected to the car/truck braking system, I have always managed to pump seized pistons out with the brake pedal while still on the vehicle. No dramas

Bob

 

[Barlidge]

I'd probably try air but I would be putting it inside a strong box.

 

[dobbslc]

Keep you fingers out the way!!!
Old rag around it all with some wood to soften the blow when it flys out!.

 

[steviec_lj]

Compressed air is fine, use common sense. I made a small rig that allows me to bolt the calliper in, and use an offcut of 38x63 to soften the ejection rate.

Petrol may rot the seals for you..

 

[8ob]

Air is ok to pop them out on the bench if they are not seized but not really a match for the 15000psi of a grease gun or the 1200psi of a brake system.

Bob

 

[zzr1200]

Still risky when the seals can blow, piston can split etc.

Compressed air at 150psi is no where near the pressure in a hydraulic brake system, you'll never cause a caliper piston to split with air pressure. I've used a portapower pump to remove caliper pistons before and they will reach 10,000psi.

 

[steviec_lj]

Air is ok to pop them out on the bench if they are not seized but not really a match for the 15000psi of a grease gun or the 1200psi of a brake system.

Bob

Was just watching the grease gun method on YouTube..

 

[Olderisbetter]

I have used air and fluid to push a stuck piston out in the past, Use a bit of timber held in place with duck tape to stop the piston flying out, Then wrap in a big rag and stuck in a nylon sack cuts the risk down, If they are a real pain warm in the oven first.

 

[Turbo]

I had caliper pistons that would go so far out but get stuck but I needed to strip them to replace the seals. I modified an old brake hose to accept an airline coupling but even with 120 psi of air it still wouldn't budge! I finished up using a chisel in the groove where the piston dust seal sits & tapped gently either side with a hammer with the air pressure behind it. I had wood & metal spacers in front of the piston so it could only travel a few mm if it suddenly went. When it did go it was fairly gentle, the spacers doing their job.