Brake fluid flush question

Today I was doing my every-2-year brake fluid flush on my BMW. I had finished with the two back wheels, and was starting on the front passenger side wheel, when I sheared off the bleed
screw on the caliper DAMMIT! So, now, there's no part of it above the caliper housing as it sheared evenly at about the housing level. What really annoys is that I was leaving for Florida in the morning in the car, but I wanted to finish the flush first. I'm gonna try to find a shop that'll get the thing out and put a new one in in the morning but may be unalbe to on such short notice. (I tried for a while doing this myself, but have finished with that attempt.)
This may seem like a stupid question, but it's not something I've thought much about: If I use the car for a couple of weeks with the front lines un-flushed, would the fluid in those lines affect the nice clean fluid in the lines to the back wheels? IOW, if I flush the front lines in a couple of weeks, will it be as good as if I'd been able to do them all today? Thanks.
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snipped-for-privacy@hotmail.com wrote:

If a BMW has only one reservoir for the fluid, then it will eventually mix. Crack the line at the caliper and bleed it that way.
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" Paul " <"=?x-user-defined?Q??= Paul
wrote:

You know, I don't think it will at lest not very quickly, it mostly travels up and down in the same spot.
We had to drill out and use an "easy out" to remove the broken bleed screw on my E36.
-Russ.
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Paul wrote:

I would *not* attempt to bleed the brakes by opening the brake line at the banjo bolt. It's hard enough to get all the air out when done correctly. Why not just fix the broken fitting and do it the right way?
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-Fred W

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Fred W wrote:

Success depends on the amount of common sense of the person(s) doing the bleeding.
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snipped-for-privacy@hotmail.com wrote:

I'd just drive the car and not worry about it, but when you do get the bleeder screw fixed might as well flush the system completely.
Theoretically the only intermixing of the fluid would happen way up at the reservoir, but it doesn't take that much more time...
just curious, does your BMW have those little rubber caps on the bleeders? I've found those to be quite useful; at least I've never owned a car that still had them that I had any problems bleeding.
nate
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Nate Nagel wrote:

Yep Nate, that's exactly what I did. I'm back now after 10 days of no Web access and no phones...bliss.
I couldn't find a shop that could fix the thing on short notice, but now that I'm back, I'm thinking of trying to get it out myself. I've got a drill, but I need a little bit that will bite into the metal, just enough to perhaps makes a couple of little notches so I could try and use a little screw driver to back the bleeder out. It's hard to believe I put it in so tight 16 months ago when I replaced pads and rotors on that car. The bits I have supposedly can be used with metal, but I can't get it to bite at all. Are there any special bits I could get that would bite?
Another thing, this bleeder is officially called a "ventilation valve" and is VERY hard to find. Dealerships don't carry them and I haven't found any on line after briefly searching. I'm surprised that they're not needed enough for them to be in stock.

Yes, they do have those little rubber caps. I guess they are to provide redundancy in case a bleeder somehow got loose, causing no brakes without one. I think that's the cause of my problem. Even though I thought I was being careful not to overtighten those little things, I did. I always have this nightmare thought of one coming loose while driving.
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snipped-for-privacy@hotmail.com wrote: <snip>
(OP snapped off a bleeder screw from a brake caliper.)

These are difficult to remove once broken. I suspect the bleed screw has seized in its hole, which is why it broke to begin with. The "screwdriver" approach sounds interesting but I doubt you'll be able to generate enough torque. You might have better luck with a screw extractor.
I have successfully removed a broken, seized bleed screw by drilling it out, drilling out the bore, retapping it a size larger, reaming the seat, and replacing the bleed screw with a larger one. However, this is one case where I recommend that you have a professional do the job. If you break off a screw extractor or drill bit inside the screw, it's all over. (Well, I suppose you could try again with a carbide bit.) If you cock the drill, the resulting hole might be too far off-center to have any prayer of the new bleed screw seating and therefore sealing properly, and without a vertical mill it will be impossible to put right.
Let a pro take these risks--if the pro destroys the caliper, it's his problem. Even if the pro won't take the risk, most have done enough things like this to be able to pull off the repair if it's possible and salvage the caliper.

This is a regular bleed screw, isn't it? If so, nearly any random auto parts store should have them. Remove the one from the other side and take it with you to make sure you get the right size. (Obviously, this requires taking a different car!)

They are useful in preventing a certain amount of corrosion from entrapped water, which could lead to the screw seizing.

The rubber caps provide NO redundancy. They will not contain the hydraulic pressure required to stop the car. They are just there to keep water and road grit out of the bleed screw's bore.
I know it's too late now, but when you suspect that a bleed screw might be seized, try to tighten it, too. Any movement of the threads will enable you to work it out by tightening and loosening it (probably many times) so the threads can be chased.
JRE
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JRE wrote:

I agree, but I thought I'd try the pipe wrench/screwdriver trick...pressing on the handle end of screwdriver while turning it with a pipe wrench... probably won't work, but what the hey.....I doubt the business end of the screwdriver will take the force without bending.

I agree again, and feel sure I'll have to let a pro handle it, but I have some doubts about him offering to replace the caliper at his expense if he can't fix the problem. I'm expecting him to say that I need a new caliper---at my expense of course.
> This is a regular bleed screw, isn't it? If so, nearly any random auto

Hmmm, I wish. I have a feeling that my local NAPA or Pep Boys wouldn't have this, but I haven't checked. A local dealership says they'll order one for me; they're almost ten bucks each.

Makes sense.

I bought a new torque wrench and will try to find a little deep socket to fit this thing so it doesn't happen again. I have a tendency to over tighten, unfortunately.
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snipped-for-privacy@hotmail.com wrote:

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It's all too easy when using a socket set on smaller sizes as the leverage is too high. Ring spanners are in different lengths according to nut size which limits the torque you can apply to somewhere near the correct amount. So if not using a ring spanner on smaller sizes and not a torque wrench (which really isn't necessary for things like bleed screws) grip the socket set handle near the pivot rather than at the end. Or use a 1/4 drive set for the smaller stuff since the handles on these are usually only about 6" long rather than more than double that on a 1/2" type.
HTH.
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snipped-for-privacy@hotmail.com wrote:

I think you already know the answer or you would not have asked the question. You will need to re-do the rear lines because some of the old fluid will mix with the new fluid given enough time and braking cycles.
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