Ok so i pulled the MC and nothing seemed to wrong besides the wires having no home, and i was kinda concerned about the play in the shaft centered on the vacuum booster that goes into the MC. So I took a few pics of the wires i dont know where they go, and the shaft in its "in" and "out" positions. And when i removed the mc no fluid was in around the shaft so i done think it was leaking. Also how do you remove the reservoir just pull? Can the seals around the bottom of the reservoir go bad and cause the pressure to be lost without leaking fluid, cause i have NO leaks and bench bled the MC and it held for about 5 min before loosing all pressure again.

The Wires


The shaft "In position"


The shaft "Out position" Should it stay straight or hang down like that?

 

Yes, the reservoir just pops in and pulls off (rocking it side to side will help remove it).
I don't believe the reservoir seals can cause the scenario you describe, that sound like an internal seal failure.
You must have a S4...that second sensor isn't present on a S5. That looks like a warning sensor in case one circuit (front or rear) ruptures and the pressure is no longer equal.

Your booster shaft is fine.
In real life it never extends that far but in any case is held centered by the rounded rod tip being captured by the slightly concave MC piston face. Kind of a "self-centering" geometry.

 

The loose wires are for the AAS = Auto Adjusting Suspension. Looks like some one replaced the MC from another car that had AAS.

 

I did not know that.
Interesting.

 

yea i have a s4, but i also have the normal and sport suspention modes? so should i worry about those wires on my new MC or screw em? and also can you tell if your master cylinder has failed internaly by taking it apart or no?

 

Part of the AAS system are the struts and shocks, if they have been replaced with aftermarket units then just screw it, the AAS will not work without the special struts/shocks. I have never driven a Rex that had a working AAS, but have read that it did not work that well.

If you have any doubt about any part of your praking system, REPLACE it. You do not want to "half ***" your brakes, your life and everyone on the road you meet depends on you stopping.

 

Not really.
Absent a catastrophically screwed up seal or major scores in the bore, a visual inspection is pretty useless.
And, once you've taken it apart, you're basically committed to replacing the seals at the very least anyway.

+1.

 

well i just replaced the MC after a MC kit replacement and cleaning and flushed my lines REALLY well and now everything seems to be working, im giving it about an hour before i put everything back together to make sure it holds pressure. Thanks Guys!