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SMP - -
The caliper is the same as the C900 rear caliper. I rescued mine, with seriously rusted bleeder screws, a couple months ago and made this post on the C900 BB about it:
http://saabnet.com/tsn/bb/900/index.html?bID=443216
If the hex is still there and mostly intact, enough to fit snug in a 6 point 8mm socket, then I'd recommend using that, and adapter up to 3/8" drive, then a breaker bar. Gives you excellent control in applying pressure, and you can hammer down on the top of the swivel part of the breaker bar and have the force conduct straight down through the bleeder screw and into its threaded area, working to crush up rust and break the screw threads free. I use this on lots of frozen things, waiting to apply my twist-loose force till just when the hammer blow hits.
What I was faced with was just stubs of bleeders, with the hex itself badly eroded away. And with the big vise grips, heat, penetrant, and gentle back and forth tapping I was able to start them turning and then they came free.
Calipers had heavy rust scale on them but boots were intact and they work fine and ebrake works fine too. I chiseled off most of the scale. Most important was inside the two outer prongs of the caliper, where the backs of the outboard pads sit. They were heavily rusted and not flat and parallel to the rotor.
You can't back bleed unless you can get the bleeder screws loose. You might be able to bleed things by cracking the brake line loose at or near the caliper. But I wouldn't bother unless the lines now have air in them; the beneficial effects of fresh fluid are outweighed by the risk of breaking something and costing more time, nasty work and money.
If one broke off you might be able to get the stub to come out with an easy out but even the best designs of those tend to expand the screw itself outward and thus jam it tighter. And if it breaks you probly already have serious rust locking the remains in place.
If it were to break and you had a replacement, your best bet I'd say is trying to drill it out. It's already center-drilled by the hole the fluid comes out of so you're way ahead there. Use gradually larger drill bits and only go in just a touch past where the shank is threaded to. Below that point the diameter is smaller and it should come out the hole once you've cleared away the remains of the old threads.
Drill till there's nothing left but the threads, use a swiss file to file out through into the caliper body in one or two places, then pick the remains of the screw out of the threaded body. Will have just the tiny vertical notch where the file went through, but shouldn't hurt at all as sealing happens down in at the beveled tip, not the threads.
Then use say a small drill bit to pick the remains of the tip out of the hole, or a magnet. Lube things and run your new screw in and out to clean up any remaining rust. Bleed by your favorite method.
posted by 71.173.75...
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