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Triumph TR6 - Removing Brake Piston

HELP...need advice. In overhauling the front brake calipers, I'm having difficutly (read impossible...so far) in getting the piston out of the caliper from either side and from either caliper. I removed the hold down spring and the dust cover, but am unable to get the pistons to move. The calipers are out of the car, and the brake system is TOTALLY dissassembled so don't tell me to hook it back up and depress the pedal. There ain't no pedal nor master cylinder either for that matter.

Steve Pike, please send your email address. I've lost it(them). dbaker04ATaol.com.

Thanks.
Doug Baker

Steve,
I used large Vise-grip pliers to grip the piston and rotate it within the bore. While twisting, I was able to slowly pull the piston up and out of the bore. Pouring some brake fluid around the piston might help lube it. Good luck - Jeff
JB Fetner

Hi Doug,

Use a grease gun ... hook up to fitting and pump away! Allow each piston to move out evenly by holding the other back using a C-clamp etc.

Cheers, Rob
Rob Gibbs

Doug-I would prefer compressed air to grease because of the mess it creates. Keep your fingers out of harm way and cover the caliper with a rag. I see stainless steel pistons in your future if there is significant pitting of the chrome on the existing ones.
Berry Price
BTP Price

Hey all, thanks for your comments. Jeff, vise-grips occurred to me, but I was hesitant becasue of the resultant damage incurred.

Brake fluid to lubricate makes good sense, but I'm apt to go back with silicone and not DOT-4. I thought of using aerokroil, but shied away due to not wanting to contaminate the bore.

Berry, got new SS pistons, etc for complete rebuild including the O ring between the caliber halves. Intend to powder coat the caliber body if I can effectively protect the bore, but I gotta get the pistons out regardless to put the new ones in. I think I'll lubricate liberally with some brake fluid, maybe use the vise grips and/or air assist and hope for the best.

Air did not get the shuttle out of the PDWS...YET!!
db
Doug Baker

Doug,
I hate to say this lad but if you are having difficulty getting the pistons out then you might have rusty bore walls. SS pistons will not fix that issue. I see rebuild in your future.
Rick C
Rick Crawford

As a rule, I prefer the compressed air approach. There are "issues" that do crop up from time to time with these cars as you go through them. Off hand it would seem that you do have a fair amount of corrossion to contend with, not too sure that I would really worry about the AeroKroil as a contaminent as some good solvent claening will get rid of it. Also remember that heat or cold can be your friend when dealing with corroded assemblies that are resistant to coming apart. A few thermal cycles can do wonders for breaking apart corroded surfaces as the parent metals and the faying surface oxides have significantly different CTEs.
SteveP

Thanks Steve. Think I'll liberally apply aerokroil and see what happens. Still gotta bead blast the area around the piston, so may go ahead and do that before removing the old ones. I think that I can mask the bore for powder coating. Hell if Nelson Riedel can do it, I should be able to too:)
db
Doug Baker

I have removed them with a bicycle pump, the kind with a lever on it, not screw on. Plug the inlet with a bolt, hold one in place with a big C clamp, and pump air into the bleeder (has to be open, of course). You can assist with a hammer and chisel if you want, you have new pistons.

The only place that would worry you with corrosion is the slot that the main piston seal (rubber band) goes in. If that's clean and no pits, it will seal fine. The rest of the bore is just there, the piston slides on that seal, the seal just sits there in the slot. (Well, it wiggles a bit.) There will be mucky crap in there that caused you to disassemble in the first place. The pistons corrode and cause the problem, which tends to suface when you push the corrosion back into the seals with new pads.

I have a really stubborn set of calipers that I may use the grease gun in the inlet method on, but as a next to last resort. The last resort will be splitting the caliper halves and drilling and tapping the piston, then using the grease gun again. Or throw them out.
Tom

I clamped the entire master cylinder, brake assy, reservoir and tubing in my vise and ran a front brake hose from the outlet on the master cylinder to the inlets on the calipers (they fit on a TR3A), first one side then the other. With a little fluid in the reservoir and a little hand pumping the pistons came out just fine with a little mess. Mine were for a TR3A but TR6 should be similar.
hjr
hjr

You could also try using a pair of big screwdrivers to try to pry the piston out of the cylinder. Just be careful to lift it out evenly on each side, making sure it comes out straight. Also, beware of your knuckles...
Steven

OK guys, I got the damn pistons out...at least from one caliber. Took 100psi from the air compressor before one popped. Reinserted it, held it with a small C clamp and took about 110psi to get the other one loose after turning it with a large pair of pliers. ANYWAY...after removing the pistons, I saw what was causing the problem. The bore is rusted down to the rubber seal, maybe a bit beyond on one bore,or it may just be dirty. Seal groove appears to be OK. Tom, based on your comment, I should be able to clean the rust away with a fine emery cloth or my dremel and polishing compound. I'm reluctant to do that for fear of introducing a failure and subsequent leak from around the new piston. What say y'all??? Should I tackle polishing up the bore or have a machine shop take care of it?

Nelson Riedel separated the two halves of the calipers to powder coat them. He sealed the bores with old pistons and masked the mating surface of the two halves. All because he thought the "o" ring would not survive the 350o curing temperatures. This remains my intent but I wonder if the "o" rings would mind the cure temp. Takes about 350o for 20 minutes or so to get a good cure on the powder. Any comments on this?

db
Doug Baker

First the o-rings, you have some "how many years old?" o-rings in there and no really good idea as to the material or its condition. I like the split and replace option there. That temp for that long is outside what those calipers would normally see and I have to question whether old seal rings would hold up.

As for the caliper bores, the absolute worst that could happen is that you get so wild with the Dremel that you had to have it sleeved, an unlikely situation. Go ahead and do it yourself.
SteveP

If your groove is pristine, don't worry. You shouldn't leave any rust or sharp edges in there, obviously. But the bore doesn't seal the fluid. The seal is on the outside (the groove in the caliper) and the inside (the piston). I would worry more about getting the big seal in place properly. That keeps the water and dust out of there (and keeps it in pretty good, too).

Anyway, the piston's smooth finish lets it slide on the seal as the pads wear. That's no problem, there's a nice smooth finish behind the seal, because you have new pistons. If the big outer seal doesn't keep out all the contaminants, and you change to nice new thick pads, when you push the pistons back in, the bad stuff can get stuck between the seal and the piston, causing a leak.

Clean out the bores with brake fluid, and put it all back together. I like the Girling red grease in moderation to let the pistons slide into the seal easier. If you are using silicone fluid, maybe they make a grease that's special for that.

It's satisfying to get those buggers out, isn't it?
Tom

Thanks guys. I'll give it all a go and report. Yeah Tom, it was rather satisfying after trying in vain to see the piston pop out. Made a helluva loud pop with 100psi behind it!!
db
Doug Baker

This thread was discussed between 31/07/2006 and 14/08/2006

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