Gah! Broken bleeder screw

Had to pull one of the rear calipers off my C900 to resolve a sticking problem. I rebuilt the caliper and threw it back on. Pads were fairly worn due to the issue, so I put new pads on. Great. For good measure I figured I'd rebuild the other side to prevent future problems. Cleaned up, rebuilt, reinstalled. Now just to bleed the system....

BERKELEY! Bleed screw snapped off under negligible pressure. I'm thinking this is going to be a drill and extract situation. Can't find my extractors of course, so I have to go buy a new set, along with new bleeder screws. Any trips before I drag out the drill and start in on this thing? I really don't want to have to buy a new caliper....

Start by purchasing a replacement bleeder screw, then study it to make sure your drilling and extracting plan and tools aren't going to berkeley up your caliper.

In reply to 02Pilot :

Don't bother with extractors, when the bleeders break off they are too tight for them. Go straight to the drill. If the bleeder broke off on a diagonal grind the stub flat before you drill. That keeps you closer to the center. If you can, use left handed drill bits and counter clockwise rotation. That gives a better chance of saving the thread to use original tiny bleeders. Up sizing to 3/8-24 US thread bleeders remains a possibility if you can't save the thread. Be careful not to damage the tapered seat in the bottom of the hole. That is almost impossibe to fix with hand tools.

I would try the extractor first with the caliper in a vise.  If that doesn't work, it's a core.  Or, if they're really hard calipers to come by, I would take it to a machine shop to drill and tap it for an oversized screw.  

No fun either way.  Success depends on whether it got work-hardened by getting knocked bumped, seized, or over-tightened.  I'll choose to believe that it will just come right out with an extractor.  :)

I don't have LH drill bits, and I'm not sure I can find them locally today. I've found replacement bleeders and will pick them up in a little while. Might get some of the 3/8-24 ones as well, plus a tap, just so the backup plan is viable. Originals are 7mm thread (not sure of the pitch); I do have a 7mm tap - hopefully it's the right pitch.

If there's room to drill and tap to 1/8" NPT on that caliper, these are a pretty good solution: https://www.pegasusautoracing.com/productdetails.asp?RecID=5210

I have had success with bleeder repair kits. The G35 had one snap on the Brembo calipers. They are $$$ to replace, assuming you can find them. Drilling and tapping were fairly straightforward. I did it on the car and pushed some fresh fluid through it to flush the chips. It has held up fine for the last 2 years, including frequent bleeds after running time trials. 

You can see the repair in this shot. 

I've had really good luck using torx screwdriver bits as extractors for things like this. A bleeder already has a nice centered pilot hole down the middle for you so I would grab the size that seems right and tap it in with a hammer and see what happens. What I like about using these is that they tend to just twist out if they can't budge the bleeder rather than snapping off and screwing you over. If (more likely when) the first one doesn't work, get out the drill and go up a size on the pilot hole and try the next largest torx bit, eventually you'll get one that works and you are back in business.

Don't over torque the new bleeder or you'll be doing this again next time!

I've had good luck with the 1/8 NPT bleeder reapair kits as well in the past and keep a couple around to get me out of tight spot when a car needs to work the next day.

Should have thought about the repair kits while I was out. Looks like I can get this one locally, so if I fail to save the old threads I can go back out and grab it.

Got the new bleeder screws and a couple of extractors just in case. No LH drill bits to be found, even at the good hardware store. I'm going to drill carefully as far as I dare, then try the Torx trick, and if that fails see if I'm willing to risk the extractor, or if I'll just go straight to drilling for the repair kit.

I've used the torx bit trick many times and it always seemed to work.

OK, I'm making progress, but I'm uncertain of how far down to drill. I've gotten most of the threads out it seems (went up to a 7/32 bit; 7x1.00 tap calls for 15/64, so I'm under that) and I can run the tap in a few turns, but I'm not sure I've gotten the whole bleeder out. Is there a good way to determine when you've drilled down far enough?

Edit: Nevermind. I finally dislodged the tip of the bleeder, which of course indicated that I had not drilled too far. Finally got that out, ran the tap down, and threaded in the new bleeder. I haven't put it back on the car yet, but here's hoping I didn't screw anything else up. Thanks for all the quick suggestions.

And it's back on the car. Still have the get the handbrake cable adjusted properly, but the caliper is in place and seemingly holding fluid, at least in driveway testing.

In reply to 02Pilot :

Well done. The reason I suggested getting the new bleeder first is so you'd have a depth comparison and would know how deep you could drill without getting into the sealing surface of the caliper body.

Well done.

A few years ago I was fighting a broken bleeder on the Suburban and when I asked the hive about it, I was told to just buy a new caliper.   Turned out GMT400 calipers are so ubiquitous they only cost $20 a piece.    And got me new seals and slides.

Re: e-brake adjustment: The little adjustment gears behind the ~12mm dust caps are great at stripping and ruining your day -- the pads won't adjust without them. I've wrecked a couple by trying to turn them when they weren't lubed well. I don't have my Bentley atm but hopefully it has something in there about lubricating the gears.

KyAllroad said:

Well done.

A few years ago I was fighting a broken bleeder on the Suburban and when I asked the hive about it, I was told to just buy a new caliper.   Turned out GMT400 calipers are so ubiquitous they only cost $20 a piece.    And got me new seals and slides.

Same here, i think i splurged on the $40 "new" caliper at NAPA.  Painted black and all, fancy!

For something so rusty, both rear calipers seem to be OK re: the adjustment gears (one of the caps had a stripped internal hex, but I got it off by pounding a 13mm socket on it). I pulled both of the toothed wheels out and cleaned them up, and the teeth all looked good. I used them to extract the pistons when I did the rebuilds, and to pull them back in when I was done, so they should be OK. I replaced one of the handbrake cable last year because it was seized up, and I've got a spare for the other side if and when I need it. I just have to get in under the lever and fiddle with the adjuster nuts.

As far as the new bleeders and thread depth, I did measure both the new ones and the hole I had drilled, but as it happens close to half the threads on these sit proud of the caliper body, so it's not quite as useful as I had hoped it would be.