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-   -   Brake Master Cylinder Failure? (https://www.miataturbo.net/suspension-brakes-drivetrain-49/brake-master-cylinder-failure-38369/)

NA6C-Guy 08-21-2009 02:54 PM

Brake Master Cylinder Failure?
 
Up till today I have never had any problems out of my brakes. Was driving back from the book store and went to stop (had just gone through a bunch of stop and go traffic, nothing then)and the pedal went about half way before it caught. Kind of startled me. The rest of the drive was cruising and only had to use them one more time pulling onto my road. It also did it then. I pumped it two or three times pulling in the driveway and the pressure came back. Would a master cylinder just fail like this, especially at only 120k miles? Any of you ever had brake master cylinder problems? I have had cars in the past that have lasted 200-250k miles and never had any brake issues. I start school Monday, and this is really bad timing for another damn problem.

I know the fluid is supposed to be changed with fresh fluid every year, something I have never done on any other car. I would imagine old dirty fluid would lead to seal failure. The fluid is a bit orange, not clear/brown like fresh stuff. I guess maybe a master rebuild and fresh fluid would help... :cry:

wayne_curr 08-21-2009 03:03 PM

Flush your damn brake fluid with some fresh super blue.

NA6C-Guy 08-21-2009 03:54 PM

Yeah yeah, I will. But that wouldn't cause a problem like I described would it? Sudden pedal loss that comes back with pumping.

wayne_curr 08-21-2009 04:29 PM

Yes it can and it will. Do you have a leak by chance? Do you ever have to top off your resrevoir?

Brake fluid wicks up moisture like a tampon in a bleeding vagina. Dirty and moisturious fluid causes weird things to happen with your brakes inconsistently like having to pump them a couple times to regain pressure when the fluid heats up. This happened to me at an autox recently. After flushing the fluid, pedal is rock solid.

NA6C-Guy 08-21-2009 04:51 PM

No leaks, never topped it off and its right at the full level like always. I know shame on me for never flushing it. Like I said I have never payed brakes much attention on my other cars and have never had issues. I just find it weird that it just started all of a sudden like that and wasn't a gradual thing. I will flush it this weekend with some super blue and see what happens. I have had a spongy pedal since I got the car, its just one system I always ignore with cars. Again I know, shame on me. :facepalm: All of the work I have done on the car and I ignore one of the most important systems. I just wish I could afford lines and AX6's at the same time. Thats probably one reason I have ignored them so long. I had plans to upgrade the brakes, but it always gets put on the back burner. I keep telling myself it can wait till I get new pads, rotors and lines.

NA6C-Guy 08-21-2009 05:10 PM

Also, when doing the actual flushing of the system, does it matter which bleeder I use to get the old shit circulated out? Don't want to have a pocket of bad fluid left hiding at the end of one of the lines, though I guess the final bleeding will fix that. I would imagine do the LR since its the furthest. I know when doing the actual bleeding for air you go LR-RR-RF-LF (that is correct isn't it?)

hustler 08-21-2009 05:31 PM

its either a bad master or a bad 1-way valve.

NA6C-Guy 08-21-2009 05:44 PM

Just drove it to the store to pick up some fluid. Seemed fine now, or at least like it normal is. I think it was just the frequent high speed stops and high temps outside today with the no telling how old of fluid. I'm not even so sure that the pedal went any further than usual earlier :giggle: I think its just one of those things I never realized, and for whatever reason something made it click in my head that "shit, my pedal goes nearly half way before the brakes engage". Either way, new fluid will go in tomorrow. If it does in fact act up again, I will just have to shell out for a new master or a rebuild kit, if you can even buy rebuild kits anymore.

Is there adjustment on the pedal for slack at the top of the pedal? Bleeding it may make it go away, but I have about 1'' of travel at the pedal face before the slack is taken up. I know you need a little, but surely not an inch.


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