Brake Master Cylinder??

thaxman

Mazda5 the Anti-Van
Went on a drive and everything was OK except on the return leg, got stuck behind a 'Burb that refused to acknowledge the gas pedal, then got into thick construction, and went from 25 mph for miles to 10-15 mph. As I ditched a left into a shopping center to escape, I hit the brakes to go over a lane that had been removed down to the subsurface, and I felt the ABS go crazy. As I got in the lot, I felt a serious decrease in brake boost, that has persisted. Basically, the pedal travels far past the point it would usually begin to bind the brakes, and nearly at the bottom of travel it eases into doing its job. They feel spongy where they start to bind, but before then, like pumping the hydraulics on a jack where the seals have gone out.
I have read before that these master cylinders give up very suddenly with no warning and I would like opinions (and most certainly experiences) that confirm for debunk this thought.
 
Actually just took it out again and it appears that the brakes are back as far as I can tell. So, could that have been chalked up to a low-vacuum issue due to near-idle rpms, low speeds and wheelchair-like acceleration?
 
Yikes! Brake pedal confidence is important...
(eek2)
How is that brake fluid? Has it ever been bled/flushed? Any freezing temps around you lately?
 
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Went on a drive and everything was OK except on the return leg, got stuck behind a 'Burb that refused to acknowledge the gas pedal, then got into thick construction, and went from 25 mph for miles to 10-15 mph. As I ditched a left into a shopping center to escape, I hit the brakes to go over a lane that had been removed down to the subsurface, and I felt the ABS go crazy. As I got in the lot, I felt a serious decrease in brake boost, that has persisted. Basically, the pedal travels far past the point it would usually begin to bind the brakes, and nearly at the bottom of travel it eases into doing its job. They feel spongy where they start to bind, but before then, like pumping the hydraulics on a jack where the seals have gone out.
I have read before that these master cylinders give up very suddenly with no warning and I would like opinions (and most certainly experiences) that confirm for debunk this thought.

Looking around the web, it seems that you may have had air in your ABS system, or one of the valves that put the ABS system into play was stuck for a while. Was any code thrown? Does it happen again if you use your ABS system?
 
I've had the vacuum boost loss in a brake master cylinder assembly before with a split vacuum hose fitting.

When that happens, your brakes feel just like when you use your brakes in the driveway with the engine turned off. Which just means you have to press the living hell out of your brake pedal to stop.
 
Weird, but all has been back to normal since. Are these braking systems computer controlled in any way? Seemed that shutting off the car helped firm the pedal a bit, and after a few hours of rest, it has been fine. And YES! I know I need a brake bleed!! I was going to see if I needed a booster before I did a bleed, since I would only have to do it all over again.
Fluid lever has never changed in the 7 years I have had this, and while we have seen some years with real freezes (below 26F IMO) this year has barely been worse than the last 2 winters, which means we got into the very high 20s a month ago, and probably won't go much colder anytime soon.
No codes, but I have to wonder about the stuck ABS valve. Again, is there a braking control unit somewhere?
Since it has come and gone, I believe my vacuum lines are still running strong.
All of this really surprised me b/c #1, the whole fam was in the car (all 6 seats) & #2 after wringing MazdaUSA dry on warranty work back in 09, the only essential system I have had go bad has been the thermostat. Everything else has been secondary or tertiary - motor mounts, bushings, shocks, interior electrics, plastic pieces, etc.
 
Went on a drive and everything was OK except on the return leg, got stuck behind a 'Burb that refused to acknowledge the gas pedal, then got into thick construction, and went from 25 mph for miles to 10-15 mph. As I ditched a left into a shopping center to escape, I hit the brakes to go over a lane that had been removed down to the subsurface, and I felt the ABS go crazy. As I got in the lot, I felt a serious decrease in brake boost, that has persisted. Basically, the pedal travels far past the point it would usually begin to bind the brakes, and nearly at the bottom of travel it eases into doing its job. They feel spongy where they start to bind, but before then, like pumping the hydraulics on a jack where the seals have gone out.
I have read before that these master cylinders give up very suddenly with no warning and I would like opinions (and most certainly experiences) that confirm for debunk this thought.
I know I posted this before, in fact pretty recently too. I just don't remember where. Anyway, on my old 2006 I started having that issue. Every time, the ABS kicked in my brake pedal would go to the floor. The darn thing still stop right but the pedal would have to travel near to the floor pan to do so. It feels weird and very insecure, sort of spongy and where is would normally start applying braking force you could actually feel a tiny bit of resistance follow by the all the way to the floor travel. I would bleed the lines and all would be good until the next time ABS kicked in or I had to hit the brakes hard enough (not triggering ABS). Then I would be back to square one. I finally took it in to the dealer and they determined it was a bad master cylinder with an internal leak given there was no codes and all other components were working as they should. They replaced the MC and all was good for the short time after that I owned it, I even triggered ABS as soon as I drove out of the dealer and I also did a few panic stops to make sure all was good. Unfortunately that was not too long because I ended up trading it in on my 2012 shortly there after. Just thought I'd share my experience with you. Good luck!
 
Then I would be back to square one. I finally took it in to the dealer and they determined it was a bad master cylinder with an internal leak given there was no codes and all other components were working as they should.

So a seal or o-ring on the piston was allowing a blow-by of pressure? Damn. I would have lost my mind figuring that one out.
 
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