99 S10 Blazer--Brake pedal turns soft and goes nearly to floor

Hello Everyone,
I recently had something really wierd happen with my '99 4-door, 4 wheel drive S10 Blazer. I was navigating the second, right-hand turn
in a pair of sharp, left-then-right turns while entering the driveway to one of my local grocery stores when my brake pedal became extremely soft and nearly traveled to the floor. Simultaneously, the red brake light on the dash turned on. Immediately following the turn I had to straighten out the steering wheel, and the brake pedal returned to normal, and the brake warning light went out. Since then all has worked properly whenever I've used the brakes.
The wierd part is that this has never happened before, and I have not been able to duplicate the problem since. I have examined both front calipers and hoses and all appears to be well. No cracks, pinch marks, leaks, worn pads, etc. This truck only has 28K on the clock, so the pads are not excessively worn. The hub assemblies are sound and have no play, The master cylinder fluid resevoir is filled to the "MAX" line, and was before this incident. There are no codes stored in the engine computer (does the braking system do this anyway?). Also, I do not recall the antilock hardware activating at all during my final right turn. I know the kind of vibration it makes. Besides I was on clean, dry pavement anyway.
I'll look a little further when I have some time. I have yet to pulll the rear wheels and check out the calipers and disks there. Still, I don't expect to find anything, and there appears to be no loss of fluid (no leaks on ground, resivoir full). I would assume that the hydraulics in this truck are cross-connected diagonally for safety. Is this right?
Anyone ever have something like this happen befofe? What did you find?
Not Dead Yet
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Bad brake hose someplace. Right circumstances it is "ballooning" with a bubble.

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On Tue, 05 Apr 2005 11:40:59 GMT, NotDeadYet

RE: the cause. I'm not sure I'm much help.
The braking system is not cross-connected, there's a front circuit and a rear circuit. If you look under the truck, you'll see only one hose to the rear axle, then it splits there. This is my 2nd s-series truck (94 Jimmy and now 2000 S-10 ZR2) and both were set up in this manner.
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i wouldn t look past the posibilty of a bad wheel speed sensor in one of the front hubs somewhat common.
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Anyone know what the final fix was for this Blazer. We have one like it and the information would be helpful. I tried to e-mail the original poster but they posted with a don't bother me address. Thanks.
Warren
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Hi Warren,
Sorry for the bogus email address....
I'm the original poster. As for the final solution to this problem, I have yet to duplicate the original problem. I have done the following: 1) Put vehicle up on jackstands and removed front and rear wheels and inspected all of the steel brake lines. Then I went over every inch of the flexible hoses. No damage or defects apparent. I even had someone exercise the brake pedal. Still no loss of braking or brake fluid.
2) Checked all of the steel lines from rear axle all the way up to the master cylinder (and anti-lock hardware). No leaks, no dents, just smooth steel tubing (with the occasional spot wrapped in wire to protect it).
3) Disassembled the rear calipers and re-greased the slides. Also scraped off most of the rust around the outter edge of the rear discs. It does seem that a lot of the rear disc braking surface is not even used by the pads mounted there. The smooth, polished area was relegated to a 1-inch band in the middle of the braking surface. Is this common? The front pads use the whole disc. Also, I could not get the rear disc/drum units off the axle. I need to exercise the mechanical parking brake a few times I guess. Anyone with tips for getting these parts OFF the truck?
4) Went out to a large empty parking lot and abused the heck out of the brakes in all sorts of manouvers. No fading and no loss of pedal height. The anti-lock system seemed to work just fine. I even tried things in reverse and in severe turns. Really, the only thing I managed to accomplish was the removal of some of my tire tread, what with all the black marks I left.
Still puzzled
Not Dead Yet
Just had a thought here. Anyone ever have one of the bolts on the caliper slides break on them. I never did disassemble my front calipers. I would just expect a broken slide to be much more apparent during braking......
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Thanks for the feedback. Some of these problems can never be solved. Would you keep my e-mail address and e-mail me if the problem and fix come back. Looks like you covered alot ground tying to fix it. Thanks.
Warren
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