Rear Caliper help needed!

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Rear Caliper help needed!

Postby baldyash » Sun 04.11.2018, 10:20

Drivers side rear Caliper.Can only turn the piston to retract it anti clockwise, but it is not going in.(REPLACING PADS) Is this the correct rotation(don't rotate clockwise) and if so why is it not going in.Im using a tool that Was ok on the other side.Theres an old post somewhere about removing the h/Brake lever and using the nut at the rear of the Caliper to wind back the piston. Any comments gratefully received
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Re: Rear Caliper help needed!

Postby Simon_P » Sun 04.11.2018, 11:42

You need to press the piston in hard at the same time as rotating it - it is possible without but there is a tool for doing this.

Yes you can take the lever off, and wind the screw but it will pull itself into the caliper along with dirt and air, then when you put the lever back on you have disturbed it and it won't adjust properly -
If you can't do it with pliers pushing as you turn, your time would be better spent going to Halfords and buying the tool.
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Re: Rear Caliper help needed!

Postby baldyash » Sun 04.11.2018, 13:26

I used the correct tool but it just rotated the piston! The other side I did first was OK and wound it correctly.
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Re: Rear Caliper help needed!

Postby dapinky » Sun 04.11.2018, 13:41

If thge brake pipe is still attached to the caliper, it may be that the piston can't retract as the displaced fluid can't go anywhere. It *should* just go back into the master cylinder reservoir, but if the proportioning valves are gummed up a bit, they may resrict 'reverse flow', so you get a hydraulic lock.

Try loosening the bleed nipple whilst you push the piston in (with a suitable tube to collect the fluid displaced) - it may work.

After 40 years of messing with cars I still haven't got round to buying a caliper wind-back tool - I know it would be quicker if I were just doing a pad swap, but as I usually take the calipers off every time I'm in there, I can manage without one. I have always managed with a flat bar (screwdriver with a square shaft) to turn the piston whilst applying pressure to retract it - or simply use a spanner on the shaft at the back..... but as said above, this can lead to problems with sealing, so best done as part of a caliper rebuild (or great care!).

One way to get enough pressure to force the piston back is to remove the caliper, re-insert the old pads and then use a length of 2"x1" timber to lever the pad against the casting to push the piston back with the other pad..... at the same time, grip the exposed part of the piston with a set of pipe grips to add some rotational force - it doesn't need a lot - just take it steady and it should be really easy.... even easier if you leave the caliper on the car for support, but remove the brake disc.
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Re: Rear Caliper help needed!

Postby Simon_P » Sun 04.11.2018, 18:13

You need to keep the pressure on the piston by also winding the collar at the same time - clockwise the collar is tightening itself, anticlockwise it is always loosening itself.
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Re: Rear Caliper help needed!

Postby baldyash » Sun 04.11.2018, 20:57

That's it! Thanks , will have a look tomorrow.
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