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Rear Brake Piston

stonking

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Hi All. I am changing the rear disc pads on my 58 plate saloon but the piston does not slide back in and there does not seem to be a way to wind it back in. Should it just push back because that is what I seem to remember. Oh, it is the offside if that makes any difference.

Thanks.
 

stellamon

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I used a g-clamp to push the piston in on mine, with the top off the brake fluid reservoir
 

stonking

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Hmmm, I seem to remember that is how I have done it in the past but it is not moving this time. I might open the bleed nipple a bit and see if it wants to come right.
 

stellamon

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Does the caliper have the handbrake fitted? Is it hollow or solid with slots in for winding?
 

Salim

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Just pushes back. May be seizing.
If it won't budge you can put a block in between that will allow the piston to come out a smidge (not enough to fall out) and gently pump the pedal to free the piston.

Look behind the boot to see if the pistons rusted. It may be time for a rebuild or new caliper
 

stellamon

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I agree with Salim, could be seized, common fault on these apparently. I used the brake pedal to force the piston out when I serviced the caliper on mine.
 

shadow2kn

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there's another way that part of being lazy I usually use on my 7th gen fronts, coz they're push back ones as well, and that is I put a spanner flat across the piston and then use the wind back tool without the winding bit at the end... and that works a treat..
 

stonking

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Thanks for all the advice. The car has done 230k so I guess another caliper for £40 would be a good investment really. Plus it is not a big job.
 

dozi

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Thanks for all the advice. The car has done 230k so I guess another caliper for £40 would be a good investment really. Plus it is not a big job.
Did you put a new caliper on? If so can you direct me to where you got it
 
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stonking

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From ebay. .Honda Accord Mk8 2008-2012 Rear Pair Brake Caliper, I brought both sides and did a brake fluid change at the same time. Easy.
 

Troy McClure

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If you go the route of a caliper rebuild (new piston, seal and boot), be warned that it's a pig to get the new boot seated inside the rim of the caliper and over the new piston. Tip: cable tie the boot to the piston as close as you dare to the closed end of the piston, then wriggle the boot into the lip on the inside of the caliper. Start to slide the piston in, carefully snip the cable tie, then push the piston the rest of the way in so it seats in the groove on the piston. First one took me about 4 hours, second one 10 minutes.
 

Channel Hopper

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The old trick with bike calipers was a scrap set of feeler gauges, snip the thinnest ones off the holder and arrange around the cylinder, before pressing in. But I would be hesitant to strip as a primary fix.

On the tourer (Mk7) I pushed back the nearside rear with the largest pliers here (water pump type), which is perfect for the job. No binding since.

Like these


 

Richard B

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So the binding brake faerie caught up with my car. I Installed new rear discs, new pads, pushed the pistons back in etc, but when I went for a drive I found that the right side rear wheel was about a million degrees and gave off that commuter-train-pulling-in-at-the-station smell.

Pulled it apart, removed the dust seal, and the piston was not in a good shape, with corrosion and pitting. I needed to fix this pronto, so online parts were not an option, and after not finding any rebuild kits or pistons in stock anywhere I opted to try find a second hand caliper from an auto parts recycler. Luckily, the 38mm caliper on the mk7 Tourer is also used on a variety of other Hondas and I ended up with a transplant from a Honda Odyssey, which was sold in AU instead of the Accord Tourer. So far, the Accord hasn't rejected the new organ.

Looking at the pitted piston from the dead caliper, it is easy to see why these calipers have a habit of binding. It seems to be nickel plated steel, and due to the rear brakes wearing only slowly the piston seal spends a lot of time rubbing on the same area, which wears through the plating, and following that, the now exposed steel spends a lot of time in the outside of the seal, where it is no longer protected from corrosion. The dust seal still protects it, but tiny amounts of dust, moisture and perhaps salt find their way past the seal over time. Once corroded the piston no longer smoothly slides past the seal, should you push it back in to fit new pads.
 

smokingman

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I have on an old Mk4 Accord just cleaned the piston to remove the obvious corrosion, then as I put the dust cover back on put some thick grease in the boot.
 

Bounder

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I rebuilt the rear calipers on my 7th Gen Tourer when I had it, I stripped the caliper completely back to bare metal and heated it with a blowtorch (burning my finger where the bleed nipple hole is), but once dried like that its easy to get all the crud out of the grooves for the seal and bellows seal with a pick and a mini wirebrush on a Dremel style tool.
Its very hard to clean it properly while wet with brake fluid.

I then packed the grooves with red rubber grease and fitted the square seal, and then fitted the bellows seal to the piston before refitting the piston.
Its a pain to fit but once fitted it gave no further trouble.

Square seals have a right and a wrong way depending on the taper of the wedge shape, they aren't truly square more a trapezoid shape which helps to return the piston to the resting position when the pressure is released on the brake.

The main cause of seizure IMHO is corrosion building up behind the seal and reducing the diameter of the opening causing brake issues.
Packing grease behind it reduces the ability of water to get in there and start the process of corrosion happening in the first instance.
Use some quality rubber safe grease on the slider pins as well, I found Motorex grease 2000 to be rubber safe and water resistant.
 

stellamon

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Is that Red Rubber grease?
Yes it is.



That piston looked beyond help, well done for saving it. Has the car been owned by somebody near - or under - the ocean ?
Looks that way doesn't it. We live where there's lots of country lanes covered in muck from farmers and others that never seem to dry out this time of year.
 

Bounder

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Its one of a few vegetable based greases, be warned that the red colour transfers to the brake fluid so the initial flush will appear red.
That Bendix stuff looks very interesting, not just one application by the looks of it. There is a ceramic grease available here in a white colour by Mintex called Ceratec which is similar to the Bendix paste.
ATE also make a paste for the pistons which is the same type of product https://images-na.ssl-images-amazon.com/images/I/71-9AYqEQJL._AC_SL1500_.jpg
 
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