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Rear brake piston will not wind back in - stuck

hondlegend9

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Hello
Went to change the rear brake pads on the Honda accord saloon 2006-2008. Disks all round.

The rear piston in the caliper is supposed to be wound (clockwise) back in with a tool.
But the piston is stuck solid, and won't turn clockwise so I can't wind it back in.

The cap on the brake reservoir is open, and have also tried with the brake bleeder screw slightly open.

It's the driver's side rear. Haven't got to the passenger side yet.

Any suggestions?
Where do they normally stick and prevent the piston from rotating, and how can I free it up whilst it is still on the car.

Thanks
 
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Channel Hopper

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Thanks for the reply.
But as mentioned this is a 4 door saloon. so piston can't be just pushed in.
Apologies, I was going on the Lucas guide below which suggests yours is the same as the tourer.


You may need to let it off the axle and soak in a bag of diesel for a while.

 

Bounder

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If its totally seized the best way is to fit a grease nipple to where the brake hose attaches and pump the piston out with a grease gun.
You will need to clean it anyway, usually the problem is corrosion behind the seal in the caliper body, once the piston is out, pop the seal and dust boot out, I like to heat mine with a blow torch until it is bone dry and then use a dremel with a brass brush to clean the grooves spotless, pack with red rubber grease and reassemble.
The grease helps prevent water from getting behind the seal and causing corrosion which grows and pushes the seal tightly against the piston causing seizure.
 

hondlegend9

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Thanks to everyone for their input.

It does say "Lucas" on the caliper, but there may be different variants of the Lucas caliper.

Where do they normally seize? The rubber dust boot is intact, so unlikely that that the piston is corroded.
My limited understanding is that the piston only makes contact with the Square rubber seal in the caliper? Could that be the point where it is seized.
- Or could the handbrake mechanism be seized and thus preventing the piston from being wound back. I am using the proper wind back tool, and it was never a problem when I did a few years ago.
 
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Bounder

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The boot can be intact and there will still be corrosion behind the boot, its only a dust boot not a water or oil proof seal.
The only way you will know is by stripping the caliper and inspecting it and possibly rebuilding it.
 

hondlegend9

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The boot can be intact and there will still be corrosion behind the boot, its only a dust boot not a water or oil proof seal.
The only way you will know is by stripping the caliper and inspecting it and possibly rebuilding it.
Was hoping to resolve it without taking it off the car.
If all else fails then there would be no other option but to undo the banjo bolt and hand-brake mechanism etc.

Apart form the piston being corroded, can it be "seized" at any other point?
 

Bounder

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What usually happens is a combination of : Corroded piston/ Corrosion behind seal/dust bellows that pushes the rubber out of the groove increasing friction and the consequent retraction of piston is poor.
Is the piston corroded externally?
 

hondlegend9

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This was the state of mine before rectifying it:

That piston looks in a bad state.

Just noticed the clamp on the brake line - I must admit I'm not a fan of that technique. Wouldn't it potentially damage the brake line.
I appreciate a lot of mechanics do it for speed and convenience.
 

hondlegend9

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Looks like the caliper is going to have to come off the car for a refurb.
I'm planning to undo the Banjo bolt, and then quickly insert a dummy bolt in it's place to stop the brake fluid leaking.
Anyone know what size the Banjo bolt is?
It's a Lucas caliper.
 

Channel Hopper

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Whatever happens you would need to bleed the pipes after refitting.

I would strap a small wine bottle in place near the shock absorber before undoing, then drop the end in as soon as you have loosened the bolt. Whatever comes out can be used again over the next day or so, any longer and it will take on water vapour to be of use.
 

Richard B

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The visible parts of the piston look ok, no corrosion, so would be surprised if it was corroded under the dust boot.
The piston is plated, and the piston seal constantly slides over the same area each time you brake. This causes the plating to wear, and as the worn area slowly moves outward as the pads wear, this is exactly where the piston corrodes. Corroded steel expands and this makes it difficult to push the piston back in - and won't work as a two-way piston if you do.

Most of us discover this effect after a pad change, with the new pads binding to the disk when the piston refusing to retract, causing significant Local Warming and ***ociated aromas.
 

stellamon

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Some, that see the state of corrosion immediately go for buying a new calliper. Which is really expensive. A refurb kit is a fraction of the cost and will rectify the problem.
Already done one of the rear and a front brake overhaul and no problems since.
 

stellamon

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The pistons on the 8th gen I have don't require winding in. To remove the seized piston , once the calliper is free of the disc, I just kept pushing the brake pedal down, then checking how far it had moved out each push.
 

hondlegend9

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The pistons on the 8th gen I have don't require winding in.
Thanks.
***uming you are referring to the rear brakes, with the integral hand brake mechanism, I'm surprised that the rear brake pistons don't require winding back in.
The hand brake mechanism may be a brake-shoe setp-up.

Yes, they will push out when the brake pedal is pressed, as that is like applying the brakes under normal operations.
 
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