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rear brake pistons


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#1 Gibbon

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Posted 17 November 2019 - 02:03 AM

Hi all I have an 85 starion project car with dragging brakes. The pistons appear to be frozen, I've done a little bit of research and it looks like they're the wind-in style, but I can't seem to get the things to move, I've got them in a vice on the bench and have given them considerable torque to no avail.

Are they meant to be wound the entire way in? Or do they also need to be pushed part of the way in too? There's no way on earth that the new pads are going to fit as-is. The park brake lever on the back of the assembly moves but the piston doesn't move with it, so I assume that means it's frozen in position. The piston is about 5mm out from being completely flush with the caliper surface, I assume it does go completely flush when fully retracted?

A few questions in there but simple enough to answer I hope





#2 markhansenconquest

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Posted 17 November 2019 - 11:14 AM

Piston moves in till its flush.........The piston has to be turned in .........Take it off and put in  a small bucket and soak in toilet bowl cleaner to break free the rust..........use lime away (gel formula )  99 cent  store...


Edited by markhansenconquest, 17 November 2019 - 11:18 AM.


#3 Gibbon

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Posted 19 November 2019 - 02:16 AM

thanks mate. I'll bring them to work and drop them in a bucket of something. Rebuild kits on the way now so no longer precious about saving the seals

#4 kev

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Posted 19 November 2019 - 03:34 PM

I've had them stick in the past.  Try spinning them out, counterclockwise, too.  I've found that they typically turn out easier than in and you can free them up.   In fact, if you are rebuilding them, that is what you need to do anyways.  

On the rebuild, you will not be able to replace the o-ring for the screw that threads to the piston without tearing the rear portion of the caliper a part.   Reassembling this isn't the easiest job to tackle, but I have a how to thread on the subject the brake FAQ forum.  

Kevin

#5 Gibbon

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Posted 29 November 2019 - 05:24 PM

Nailed it, finally. I bought (and bent) a winding tool. Ended up throwing both brakes in the oven then tapping the piston around with a hammer and drift

Edited by Gibbon, 29 November 2019 - 05:25 PM.


#6 Gibbon

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Posted 01 December 2019 - 01:22 AM

Amazing how little rust caused the pistons to lock solid. The pistons came up fine with a bit of scotch brite. Checked the handbrake cables are nice and free too, which is a godsend.

Then one of my guide pins went missing, last seen in the hands of a certain young child....

Is it safe to bead blast the rust off of the inner bore of the caliper? I have a rebuild kit for the seals.

Edited by Gibbon, 01 December 2019 - 01:37 AM.


#7 Ressurect1on

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Posted Today, 04:17 PM

if you do you need to take a hone to it after, similar to when you hone out a cylinder.




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