TR2/3/3A TR3 brake caliper rebuild

[Dan_Pasta]

I am rebuilding the brake calipers on my 59 TR3A. They are currently removed from the car ..... and you'll never guess .... the pistons are stuck tighter than a drum. Any "tricks of the trade" to get them out?
The brakes are the Girling style .... if that makes a difference.

 

[Mickey Richaud]

Hi, Dan -

When I've had to pop pistons loose, I've found that soaking them in WD40 or PB Blaster over a day or so, then clamping the caliper securely in a bench vise and forcing compressed air through the fluid inlet usually works. Be very careful, though - cushion the thing with an old towel or rag, and be sure not to get your fingers anywhere near the piston. Also, be sure the caliper is covered with the towel, so nothing flies out that shouldn't. I've done this several times, and if the piston hasn't completely become one with the caliper, it usually works.

Mickey

 

[Geo Hahn]

A popular trick (though one I have not had to resort to) is to fit a zerk to the open hose connection and use the pressure of a grease gun to force them out. Sounds much safer than air pressure. I would think you would want to stop whichever one moves first (e.g. C-clamp) and get the other one moving too before finishing up.

OTOH, if there is a bit of piston sticking out, some just grab it with channel locks and twist & pull. In that case you probably won't be reusing that piston, but new Stainless Steel pistons are nice to work with.

 

[svtmikey]

I always use compressed air the caliper (where the brake line would attach). An air blow gun with a rubber tip usually works but CAUTION....make sure the piston is not pointing at you or anything you want to keep...sometimes it "pops" out with quite a bit of force.
I put the caliper under a welding blanket, then hit the air button. It also might be an idea to start with a lower pressure..I never do of course, but it would be a good idea.
Mikey

 

[Tinkerman]

Hi:
Had the same problem, tapped them out one silly inch at a time. I have decided that it is better to buy some rebuildable ones and use those. I have not tried the ones that I rebuilt yet. I suspect that they are not going to hold when I hit the brakes! You cannot scrimp on safety!

Regards, Tinkerman

 

[Banjo]

I've used the old blow gun trick too, and used the channel locks, and chiseled them out inch by bloody inch.
If they're stuck, you need new pistons. so don't worry about saving the old ones.
also, there is a big debate over seperating the two halves of the calipers. Moss says "don't, there are no known torque specs to reassemble them" but they sell the replacement "o" ring.
I've personally seperated them before, and just made sure the torques are even side to side without problem.

 

[Alan_Myers]

Hi all,

Good suggestions already...

I recently undertook rebuilding a very neglected set of TR4 calipers and found air pressure (up to 120 psi) wouldn't budge the seriously frozen pistons. But, the grease gun trick worked well, though there is always a lot of wasted grease! I did have to modify the grease zerk with a die, cutting straight 3/8" x 24 threads on it. I think it had 3/8" fine pipe threads (tapered), which wouldn't thread into the caliper at all.

The grease gun method moves the piston out slowly, so there is no danger of it going flying. With the air pressure method I usually slip a piece of wood in between the two pistons, and/or just leave the brake pads in place temporarily to keep one piston from smashing into and damaging the other. Done right, the first piston can be loosened part ways, just a little but not removed completely, and clamped in place to transfer pressure to the second piston.

Otherwise, if the first piston pops all the way out and the second one is still stuck firmly in the caliper, now there's a gapping hole where the first one was and no apparent way to get the second piston out. When this happens, to seal the first piston hole up, I have a wide, flat scraper tool that I slip in there with an 1/8" thick piece of flat rubber under it, then tightly secure it all in place with a pair of c-clamps to form a seal.

With air, that's usually all that's needed to release the second piston. But, if using grease on a more stubbonly stuck piston, I've found it necessary to use a couple extra straps of steel under the c-clamps to reinforce the thick, but flexible blade of the flat scraper tool and achieve a really good, tight seal. Otherwise, the grease just lifts the blade and oozes out around it.

It works, but I just hope no one ever films me trying to juggle all the pieces and get them clamped in place /ubbthreads/images/graemlins/lol.gif

Now, if anyone has any suggestions for freeing up some *seriously* frozen bleeder screws /ubbthreads/images/graemlins/nopity.gif, I'd love to hear 'em!

One bleeder screw is sheered off flush with the caliper body (Previous owner did that. Still, I can get good grip on it with a screw-extractor). The other is starting to round off on the shoulders of the hex and I worry about snapping it off as well. I've tried soaking with WD40 for about 2 weeks, and more recently have had 3-in-1 "Professional High-Performance" Penetrating oil on them for a few days (the local guys didn't have an PB Blaster /ubbthreads/images/graemlins/frown.gif).

I've tried tapping and whacking /ubbthreads/images/graemlins/hammer.gif, as well as the old "tighten before you loosen" trick. Still no luck and no movement so far.

Please submit suggestions before I resort to the ocy/acetylene torch or maybe some sulphuric acid /ubbthreads/images/graemlins/devilgrin.gif.

I know, I know... I should just pitch these calipers and look for a better set, if I must have the spares. Hey, it's the Scotsman in me that won't let me do that! These are in good shape overall, especially the bores. A pair of new speed bleeders and new stainless steel pistons are all that's needed to fix them up... if I can just get those damned bleeder screws out!

Dan, let us know when you start reassembly and wonder how to get the new dust covers on! (Hint, it's sorta like catching a greased pig /ubbthreads/images/graemlins/wink.gif)


/ubbthreads/images/graemlins/cheers.gif

 

[Banjo]

Alan. Personally I woulden't be so hesitant with the "sparkle wrench". They work very well. But try applying some brake fluid to the threads. I'm not sure how it will work on bleeders but it's a remarkably good remedy on other stuck bits like O2 sensors.
other than that just the normal PB Blaster or your favorite penatrating oil.

 

[Andrew Mace]

[ QUOTE ]
...Now, if anyone has any suggestions for freeing up some *seriously* frozen bleeder screws /ubbthreads/images/graemlins/nopity.gif, I'd love to hear 'em!

One bleeder screw is sheered off flush with the caliper body (Previous owner did that. Still, I can get good grip on it with a screw-extractor). The other is starting to round off on the shoulders of the hex and I worry about snapping it off as well....Please submit suggestions before I resort to the ocy/acetylene torch or maybe some sulphuric acid /ubbthreads/images/graemlins/devilgrin.gif.

[/ QUOTE ]My best success has almost always been with heat, although I tend to use a propane torch, which is more than enough heat for this sort of job. It's trickier on a caliper to heat just that little area around the bleed screw without melting something else (like an internal seal /ubbthreads/images/graemlins/nonono.gif), but it can be done. Piece of cake on a wheel cylinder, though, since they're more easily disassembled!

 

[martx-5]

At work here (I work for an electrical and caliper rebuilder), we clean with heat in an oven. When we have stuck bleeders, we just leave them in, as after the heat cleaning, they will all come out. We clean at about 850 degrees F. So heat works very well.

If you're faced with a broken bleeder, we have found only one successful way of dealing with those, and easy-outs aren't on the list. You WILL break the E-Z out off, and being made of hardened material, makes it virtually impossible to do anything with. Time to chuck the caliper. /ubbthreads/images/graemlins/hammer.gif Drilling becomes the only viable alternative to that broken bleeder. However, there are a few things you need to be aware of before you start drilling. Those bleeders are much harder then your typical high speed drill. Cobalts might work for one or two bleeders, but carbide tipped drills are really the only ones that will be able to consistently drill out those bleeders. Of course, a drill press and proper clamping will be neccesary to get a straight track on the bleeder. We use a drill size that would be equivalent to the tap size for the bleeder. If the setup is reasonably straight, the drill will follow the hole down the bleeder. Eventually, you will get to the cross drill in the bleeder. Most of the time, it just grabs and spins the tapered end of the bleeder and you can shake it out. Sometimes when it grabs, it snaps the carbide tip of the drill. Going slow will prevent that problem. If you've done everything right, all that will be neccesary is to chase the threads with the original size tap and install a new bleeder.

If it's begining to sound like it's not worth drilling out a broken bleeder, you are probably right. It might be best just to get a rebuilt replacement. Also, as a rebuilder, we will accept cores that have broken bleeders, but will NOT accept cores with broken easy-outs or drill bits. I'm sure most rebuilders have the same policies. /ubbthreads/images/graemlins/thirsty.gif

 

[trfourtune]

heat,heat,heat. quench also may help but you cannot go too hot or you will ruin the metal (crystall structure of the metal). for really stuck pistons this works also but those rubber parts are going to smoke. i wouldn't be too worried about separating the halves as long as you torque evenly to about 100 ft lbs and surfaces are clean and flat (check flatness).
rob

 

[billspit]

After soaking mine in every solvent known to man, I used the grease gun trick. It worked like a charm, but as stated above, threads didn't match. Mine went in just enough to work. Then you get to dig out all the grease.

 

[trfourtune]

just remember that the internal seals between the halves have now been exposed to "every solvent known to man" and are probably junk now. soaking ruins the rubber as well.
rob

 

[mrv8q]

Hey, Dan, I'll pipe up here, as I was where you are are on my '59 TR3 last year at this time. I'll agree w/ Geo; The grease gun trick really works well... slow, but messy. I had no trouble screwing into the fitting though; squeeze, and out they came. No solvent issues this way, just clean up!

Where you're headed for fun, though, is putting the pistons back into the cylinders. Now, there is an excercise in futility! I eventually gave up, and found a place to put them in for me. After 45 years, 1 seal was completely toast.
Now is a good time to order new brake hoses, it you haven't already. Braking, it's a good thing!

Best, Kevin Browne
'59 TR3A #58370

 

[shorn]

When I removed the stuck pistons from my calipers, I did not have compressed air in my garage. First, as above, I soaked the pistons with PB Blaster for a day or so. After trying to remove the piston with pliers, channel locks, and tapping with every object in the garage to slightly loosen the pistons. With the caliper removed from the car, I rehooked up the brake line (left the other caliper on the car) and simply applied the brakes. Used C clamps so as not to have one piston come completely out before the other loosened. Anyway, the hydraulic pressure of the brakes put enough pressure on the pistons to work them loose.