Brake have been sitting since 1990 - replace or rebuild?

[Foxie]

When I was rebuilding my calipers I made up this "brakebuster" from an old foot pump and an old 7/16" master cylinder.

Standing on the pedal with my full weight gives a line pressure of 2,666 psi, or around 90 Bar.

Never failed to shift a stuck piston.

[69S4]

I welded a grease nipple to a bleed nipple and use a grease gun to move stuck pistons

[2cams70]

Before removing the calipers from the car I remove the piston rubber boots and the brake pads and pump the brake pedal (whilst keeping an eye on the brake fluid level) until the pistons move outward and just contact the disc. Only then do I disconnect and remove the caliper. After removing if you bang the caliper a couple of times on a block of wood the pistons will usually just fall out.

I've never separated the caliper halves. Never had a need to and never had a problem. Unless the hydraulic circuit has been contaminated by mineral fluid or you've used a mineral fluid to clean parts with the rubber seal between the two halves should never need to be replaced.

Always use only methylated spirits and/or water to flush and clean brake parts and you won't have a problem. Grease unless it's rubber grease gives me the shivers!! If you intend to store your rebuilt parts for a while or even if you are not use rubber grease in preference to brake fluid as an assembly lubricant because the brake fluid will pull moisture out of the air during storage and cause your freshly rebuilt parts to corrode.

[2cams70]

Further to this - when you remove the pistons you'll usually find a ring of corrosion in the caliper bores sitting just above the piston seal. I clean this are with some wet and dry to remove as much of it as possible. The corrosion here is caused by road water thrown up by the wheel getting underneath the piston dust boot - more so if it's torn or damaged. Sticking of the piston caused by this corrosion is the primary reason for unbalanced left/right braking. When you reassemble pack under the dust boot with rubber grease to hopefully reduce the chances of corrosion occurring in this area.

[klfulop]

Can anyone give a definitive answer as to what color the plating was originally on the caliper halves ?

I know the Germans were using a yellow/gold colored zinc dichromate plating by the 1970s. Were Lockheed and Girling doing the same ? Or was it a silver plain zinc plating ?

[oldelanman]

Can anyone give a definitive answer as to what color the plating was originally on the caliper halves ?

I know the Germans were using a yellow/gold colored zinc dichromate plating by the 1970s. Were Lockheed and Girling doing the same ? Or was it a silver plain zinc plating ?

My S4 front calipers have never been replated or painted ....

S4 front caliper

[klfulop]

Thank you for that !

[512BB]

I am reliably informed that the original surface finish on calipers at the time was cadmium plating, now banned in Cambridgeshire

I am at a loss as to why people like Classicar Automotive gold passivate brake parts today, when it looks gastly and only lasts 10 minutes. Surely zinc plating would last a lot longer and look far more original, but I suppose it would cost 10p more!

Leslie

[nmauduit]

I am reliably informed that the original surface finish on calipers at the time was cadmium plating, now banned in Cambridgeshire.

Quality plating is getting difficult to obtain in many places : I believe ZnNi is an (possibly higher resistance) alternative to Cd plating (used to be common for quality fasteners, like on BMW bikes), but it involves a trivalent chrome step and chromium is a component that is even more difficult to get applied thesedays...

[tdskip]

Hello and to anyone I missed belated happy New Year!

Some progress report on the front calipers. The pads came out easily but the Pistons are not cooperating. I tried to press there and only one of the four pistons came out.

I split the calipers without too much effort and I am glad I did as one side had a bad rubber seal where the fluid pathway meets on other side. Even with the calipers apart I was not able to budge the remaining pistons.

Looks like I need to reassemble and try grease next?

[USA64]

I put mine (I think already split) in a pail of solvent, either derust or carb cleaner, I forget which, for a few days. When I took them out, I put them in a vise and grabbed the exposed piston with a pair of vise-grips, hard as they were not being reused. I applied a turning torque to the pistons just trying to rotate them. Once they began to move I rotated them back and forth until they moved fairly easily. Once that was done they pulled out with no pressure required.

[StressCraxx]

Hello and to anyone I missed belated happy New Year!

Some progress report on the front calipers. The pads came out easily but the Pistons are not cooperating. I tried to press there and only one of the four pistons came out.

I split the calipers without too much effort and I am glad I did as one side had a bad rubber seal where the fluid pathway meets on other side. Even with the calipers apart I was not able to budge the remaining pistons.

Looks like I need to reassemble and try grease next?

Hello Skip,

There's a non toxic de-rust chemical available that works really well, called "Evapo-rust". https://evapo-rust.com/

That should help with removing the rust and helping remove the pistons.

[alan.barker]

I've just looked for the details where i bought stainless caliper pistons from in USA.
The details are "John Farrell Autos Works", West Babylon, New York 11704-1037.
I live in France so if from USA or UK there is always postage.
On John Farrell's site there is car parts then on list Pistons for other Cars.
The stainless Pistons i bought were for the rear Calipers on my Elan Sprint
Alan

[Donels]

I successfully removed one very stuck piston by filing two deep grooves in both sides. Then use the grease method and rotate the piston at the same time via a bar in the grooves. Pressure and rotation freed it.

[tdskip]

Thank you gentlemen, looks like I have a path forward here.