Brake caliper pistons

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StoneyMR2
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Brake caliper pistons

Post by StoneyMR2 »

Hi guys, New member and new MR2 owner here.

I've recently purchased a mk2 and so immediately join this forum. It's come in very handy so far but now I need a little advice.

The car had been sat idle for 10 years with its last mot back in 2009. Engine runs, gearbox seems OK ( I was able to drive it on to the recovery truck) and most electrics work, lights etc. Front brake calipers were off the car when I bought it and the pistons were pretty well seized in there. I've mamaged to get them out but there's a bit of corrosion around the top of the bore

Have these calipers had it, or is there a way clean them up?

Any help, suggestions and advice would be much appreciated.

Thanks.
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jimi
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Re: Brake caliper pistons

Post by jimi »

Get them bead blasted or clean it up with rotary wire brush, light corrosion on the calipers isn't bad, it's the pistons that matter as the seals are fixed in the caliper and the sealing surface is the piston body.You can buy seal kits and new pistons from Bigg Red or you can send them to Bigg Red and they will refurbish the calipers for you at a reasonable price. They do an excellent job.
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Re: Brake caliper pistons

Post by MR2DI4 »

Yeah I have cleaned some up like that but it takes ages to do yourself but I used some dental tools and some rust neutraliser called Jenolite.

The pistons can be reused if there are only tiny corrosion pits. The piston seal is 3 or 4mm wide so leaks are only going to happen with serious pitting.

You kind of need to know what your doing when it comes to brakes or else get it done professionally by someone fitting some refurbished calipers.

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Re: Brake caliper pistons

Post by jimi »

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Re: Brake caliper pistons

Post by StoneyMR2 »

The pistons were looking a little worn but I was planning on replacing all parts with a rebuild kit anyway.

My main concern is at the top of the bore where the where the last boot/seal sits. If I scrap out the rust will it affect the efficiency of the seal?

Thanks for your help and advice, I'm finding this forum invaluable.

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Re: Brake caliper pistons

Post by jimi »

The outer seal is basically a dust seal and will be fine once the groove is cleaned out. The important one is the groove below that where the piston seal sits, as long as it's clean and free from any major pitting it should be fine. If there's any heavy wear or pitting on the sides of the pistons I'd replace them.
IIRC Bigg Red also sell stainless pistons.
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Re: Brake caliper pistons

Post by peteV6R5 »

jimi wrote: ↑
26/03/20 1:10
http://biggred.co.uk/
its worth checking out the bigred site fully.
As complete refurb and colour of your choice (diff costs depending on colour) is very reasonable.
plus they know what they are doing and when completed comes with warranty.
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Re: Brake caliper pistons

Post by m122794 »

+1 for Bigg Red.

Got them to do mine when I was rebuilding 4 years ago and they're still perfect. Have used them since and for the price, they do a fantastic job.


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Re: Brake caliper pistons

Post by StoneyMR2 »

I'll give them a look. Thanks guys.

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Re: Brake caliper pistons

Post by abovetherim »

As Jimi said the rust above the piston seal is not an issue.
To get rid DIY, you can use some harpic 10x and some scotchbrite. Just rinse off well and wear gloves.
When it come to the rear calipers you will have other issues! The handbrake mechanism gets seized as the seal on the pivot let's past moisture and it rusts behind. The piston can also seize if it's not been use (they screw in/out).
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