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the master cylinder has two stages to it for the primary reason of having a back up if the first stage fails for some reason. The ABS valve is for sure an interesting possibility given from the sounds of it your master cylinder could be OK and you could still have a case where the brake pressure is dumped if this Valve is acting up.

Report back on the shops findings - you won't be the only one who comes across this I'm sure of that. ;-)
 

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If this is the case then the NTSB should be notified, because this is a serious malfunction that could lead to deaths!
If it were common yes - but with older cars you never know what type of use - maint and conditions might cause it which case NTSB really doesn't need to be informed. If it were a new vehicle yes. An old one with lots of unknowns not really. But given people like to hold on to their old subarus for a long time always good to post results of odd ball mechanical things so others can sort it out if they come across it.
 

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I disagree with this, if this valve can fail and cause someone to loose the breaks it is a serious problem, that is one of the reasons they made all car manufactures put dual master cylinders in cars, so if it fails you still have partial breaks! This valve failure sounds like a design flaw that should be brought to their attention. Their should not be any one part on a break system to cause the whole system to fail totally!
Your assuming one failure in the case of the valve I'd bet that it involves multiple failures to cause this valve issue given as you pointed out the multi stage master cylinder is there for a reason. If the valve is the cause its probably due to multiple failures leading to this. No different than driving around with a low squishy brake pedal and a funny brake light that goes on and off on the dash at times then eventually having zero pressure given the second stage of the master cylinder which was in use and the only stage working finally failed etc.

Till the actual issue is known no sense in making it a Federal case LOL
 

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I missed his post #5! Even if the ABS light comes on the braking system should keep working! The braking system on a vehicle should be of a fail safe system, which means when the system fails it is in a safe condition (ie being able to still apply brakes but maybe of a lessor force) not to totally loose the brakes while the car is still moving. The ABS system should just be in bypasses mode when the light activates and the brakes syem should still work!
Isn't this valve you are speaking of part of the ABS (Anti Lock Braking System)?
The most over engineered consumer products on the planet are vehicles and cell phones.

If enough parts fail eventually something stops working - when your ABS light comes on you check into it ASAP! You don't drive around for a year occasionally saying hmm I should check into that at some point but heck the car seems to be working OK so - on we go.

LOL nothing can be built with infinite number of fail safes.
 

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You are wrong about this and breaking systems.
When Westing House designed Air brakes it was mandatory for the brake system to be designed as a Fail Safe system. In the system you had to supply air to release the brakes not apply air to make them work.
As far as i know, the design of ABS (Anti Lock Brake Systems) are to fail in a non-operational mode (system does not operate the pulsing function) and the hydraulic braking system is to work as though no ABS on vehicle! If the light stays on the owner is to have the system repaired, if the owner does not have the system repaired the only thing that doesn't work is the ABS system!
Now you guys are saying because he didn't have t looked at and the possibility of the Wheel speed sensor not being installed or failing the system has had a catastrophic failure! This is definitely a design flaw by the rules of safety system design! If the ABS light requires this type of attention then the vehicle should not be able to be driven!
I have been designing fail safe system for many years, and I can assure you that their is something wrong in this stem of the design of this system!
Define Drama Queen for us. Might shed some light on your view on this subject.

No seriously if you think Subaru is different than all the other Auto makers out there in regards to this LOL -- your missing the bigger picture. As we have already pointed out.
 

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Well I have been working on vehicles for a few decades, and I have never seen a vehicle loose brakes after the ABS light lit!

So can you tell me when you have seen this issue before, tell me the vehicle and the problem?

I have driven many vehicle with the ABS light lit and the only thing that has happened is the the ABS brake system activated and the vehicle took longer to stop due to the brake system pulsing.
And you have no idea what the issue is here do you - nor do I. So really all your doing is making a bunch of noise about details no one has yet. Heck for all we know a brake cylinder has failed in a spectacular way and history shows Uncle Ed fixed some issue with the brakes 3yrs prior but nothing was ever said about this. If you think Subaru brake systems are special and any different than Honda or for that matter all the other makers LOL - - Subaru isn't that special.
 
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