Removal of seized caliper pistons.

[Neil Spooner]

I am currently restoring my Elan S3 and found both front and rear caliper pistons almost immovable.
I came upon this idea that worked very well.
I cut off a brake hose end that goes in to the banjo fitting at the caliper, drilled it out and tapped it to accept a grease nipple. By using a high pressure grease gun I was able to push out both pistons to their limit by placing a thick piece of steel in the middle of the caliper to arrest the maximum movement of each piston. Warming the caliper helped.

[Craven]

Works well but make sure the cross drilling between the two halves is clear of grease.

[bitsobrits]

An old trick I learned some 50 years ago. It is effective, but does require you do a really effective job of cleaning out the internal passages of all the grease. Note that use of any kind of solvent may compromise the internal O ring between the caliper halves. Probably time for a disassembly and re-plating, with subsequent replacement of the O ring.

[2cams70]

It's a bad idea to use grease unless you plan to split the caliper halves and replace the cross seals. The grease will attack any rubber in the brake system. Normally the cross seals last indefinitively if there's been no mineral oil contamination. A better and easier method is to pump the caliper pistons out naturally on the car before disconnecting the brake lines. By strategically removing and replacing pads one at a time you can direct the hydraulic force to whatever piston you want to force out. Once the pistons are mostly forced out it's usually easy to knock them out the rest of the way once the caliper is unbolted and removed from the car. To knock them out the rest of the way you can knock the caliper on a block of wood on the opposite side to the piston you wish to get out.

[reb53]

Fortunately I've not needed to do this but was wondering what would happen if you filled your grease gun with brake fluid ?
No grease would need cleaning out then.
Brake fluid a lot thinner than grease but the gun is essentially a hydraulic pump.

[512BB]

Curious as to what finish you have on the caliper Neil? It cannot just be a blasted caliper as the banjo is brass, but that has gone caliper colour. It is close to cadmium.

Just a note to everyone. Now that Jeff has taken my advise and added several more categorys to the board, perhaps people will now start their threads in the correct one.

'Elan Discussions'
Stories, Restorations, Photos, History and general discussions about the Elan, NOT YOUR ELAN. At least not the repair of.

'All questions related to repair, maintenance, troubleshooting and parts should be in the detail forums by functional area below'

A happy Christmas to all.

Leslie

[Neil Spooner]

Thanks for your input guys.
On this car the brake and clutch master cylinders were also seized, otherwise it would have been relatively simple to get the pistons moving and remove them.
Yes, completely cleaning out the grease is vitally important. The best solvent I have found for this is Avgas, it is much kinder to all soft components and smells great too !
I shot blasted the callipers and sprayed them with Rust-Oleum cold galvanising spray.

[Neil Spooner]

….and yes, sorry, I should have posted this elsewhere. Please feel free to move it if it’s a simple task, or I could repost it myself.

[Neil Spooner]

Fortunately I've not needed to do this but was wondering what would happen if you filled your grease gun with brake fluid ?
No grease would need cleaning out then.
Brake fluid a lot thinner than grease but the gun is essentially a hydraulic pump.

I don’t believe that the grease gun has tight enough seals etc to hold brake fluid. I used a low viscosity food industry grease.

[Neil Spooner]

In the bead blasting cabinet

[nmauduit]

Fortunately I've not needed to do this but was wondering what would happen if you filled your grease gun with brake fluid ?
No grease would need cleaning out then.
Brake fluid a lot thinner than grease but the gun is essentially a hydraulic pump.

indeed... I've had to use the trick once when the 8-10 bars of air pressure off the compressor was not enough, and did it with brake fluid pushed by a manual hydraulic pump (like one finds in hydraulic bottle jacks).

People dealing with older Citroën will know about "Testiboule" devices meant to check hydraulic spheres, some are using a power steering or other hydraulic pump powered with an electric motor, I just have the plain hand actuated one.

Testiboule Citroën for manual hydraulic pressure testing

[JonB]

All seems a bit fiddly to me.

I took out my caliper pistons using the brake master cylinder, which despite having horrible leaks around its knackered seal, still managed to push the siezed pistons out. Just mounted on a vice with a flexi brake pipe to the caliper and brake fluid. Sitting the caliper in a deep tray to collect the inevitable mess. I was able to exert enough pressure on the master cylinder just pushing a rod into the piston end, so no need to rig up a pedal. But I've seen a setup that does just this with a wooden frame and spare master cylinder.

In any case, I wouldn't use grease. Apart from possible damage to the cross seal you have to use a solvent to get it out and even then you cannot be sure it's all out unless you split the calipers.