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The mkiv Supra Owners Club

How to check for sticking/seized brake pistons?


kjgreen3
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As titled I want to know the easiest way to check for individually sticking pistons on jspec 2pot and 1 pot calipers.

 

I have searched and found 'how to refurb' answers but nothing about how to check for it.

 

 

Is it a matter of taking a caliper off to see piston movement then gently pressing brake pedal and seeing if it moves out?

 

Or GENTLY pulling/rotating a piston with grips or pliers (maybe taping the ends to prevent scoring) and seeing if it moves freely?

 

Or any of the above to bring piston out and checking for corrosion or leaks on the piston.

 

 

I'm halfway through refurbing JUST the sliding calipers (and painting them :) ) just want to check the operation of the pistons before it all goes back together.

Anyway with any experience of this would you be so kind as to share your thoughts.

 

Cheers,

 

PS. I know many people may say just refurb the seals and pistons but as this is a very important area of the car which would be very dangerous job in inexperienced hands to carry out incorrectly, I would rather check they all work before having to send them off to be professsionally refurbed. If they all work then I would rather leave it at that. Also bleeding the brakes again is a right PITA, as I've found out :rolleyes: (Damn ABS unit and its love for hording air).

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If you take the pads out and carefully press the brake pedal to extend the piston by say 15 mm, you should be able to push it back with your thumbs without too much effort. With two pistons, or four, you may need to have a helper to use a lever to stop the freer pitons coming out before the stickier ones. Even on new calipers one piston will nearly always come out in advance of another. Once you have done a few calipers it's easy to see when a piston is actually seized rather than just a bit slower to extend than a pairing. If you intend refurbing a caliper USE THE HYDRAULICS OF THE CAR'S BRAKES to extend all pistons as far as you dare without them coming out of the seals. The hydraulics are VERY powerful and it is far easier to extend seized pistons like that, ready for full extraction, rather than trying to pull them out on the bench. HTH.

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Oops can a MOD please edit my thread title and put a question mark at the end. Otherwise it looks like I'm doing a how to guide rather than asking a question.

 

Cheers me-dears

 

You can edit the title yourself if you edit the first post ;)

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  • 2 weeks later...
If you take the pads out and carefully press the brake pedal to extend the piston by say 15 mm, you should be able to push it back with your thumbs without too much effort. With two pistons, or four, you may need to have a helper to use a lever to stop the freer pitons coming out before the stickier ones. Even on new calipers one piston will nearly always come out in advance of another. Once you have done a few calipers it's easy to see when a piston is actually seized rather than just a bit slower to extend than a pairing. If you intend refurbing a caliper USE THE HYDRAULICS OF THE CAR'S BRAKES to extend all pistons as far as you dare without them coming out of the seals. The hydraulics are VERY powerful and it is far easier to extend seized pistons like that, ready for full extraction, rather than trying to pull them out on the bench. HTH.
How far in mm would you say is safe before the caliper pops out,
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If you take the pads out and carefully press the brake pedal to extend the piston by say 15 mm, you should be able to push it back with your thumbs without too much effort. With two pistons, or four, you may need to have a helper to use a lever to stop the freer pitons coming out before the stickier ones. Even on new calipers one piston will nearly always come out in advance of another. Once you have done a few calipers it's easy to see when a piston is actually seized rather than just a bit slower to extend than a pairing. If you intend refurbing a caliper USE THE HYDRAULICS OF THE CAR'S BRAKES to extend all pistons as far as you dare without them coming out of the seals. The hydraulics are VERY powerful and it is far easier to extend seized pistons like that, ready for full extraction, rather than trying to pull them out on the bench. HTH.

 

Cheers Mr Wilson very helpful as always, much appreciated.

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Usually the thickness of two new pads including their backing plates but don't shout if it comes out of the seal.... :)
Thanks for that, no problem if it pops out , was just going to try and clean it up with some 800 grit while it was poking its head out , just a temporary measure untill i get new ones off you.
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