Intermittently brake pedal goes to the floor while driving

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chrisshara
First Gear
Posts: 164
Joined: Thu Apr 26, 2012 1:41 pm
Location: Middletown, CT

Intermittently brake pedal goes to the floor while driving

Post by chrisshara » Sun Mar 13, 2016 10:07 pm

Hi everyone,

Sporadically, maybe once or twice a month, the brake pedal will go to the floor when trying to come to a stop. Not losing any brake fluid externally. Seems like a master cylinder issue. But I personally have only experienced permanent malfunctions of the brake master cylinder; as opposed to this sporadic issue. Just putting a feeler out there to see if anyone has experienced this. If not, I will proceed with master cylinder replacement. I did replace the master cylinder once before; for a different issue and I also installed the GrimmSpeed master cylinder brace.

Thank you,

Chris
94 Legacy GT
95 BMW (E36) 325ic
81 BMW (E12) 528i
04 Outback
02 Acura TL Type S

mike-tracy
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Location: Des Moines, Wa

Re: Intermittently brake pedal goes to the floor while drivi

Post by mike-tracy » Mon Mar 14, 2016 6:15 am

See if the check valve in the hose going between the brake booster and the manifold is possibly leaking the direction no air should go. I think I remember having that before. But more likely the MC is the culprit.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

chrisshara
First Gear
Posts: 164
Joined: Thu Apr 26, 2012 1:41 pm
Location: Middletown, CT

Re: Intermittently brake pedal goes to the floor while drivi

Post by chrisshara » Mon Mar 14, 2016 3:53 pm

Hey Mike,

Thanks for the advice. I did have the issues with the check valve freezing and I had to give the valve a blast of WD-40 and some other solution to rid the valve of moisture (maybe dry gas) ? Maybe it's time for a new valve ? ...if they are still available ?

Having a hard time finding the pipe that has the check valve inside of it on the online electronic parts catalog. If anyone could provide the part number, that would be appreciated.
94 Legacy GT
95 BMW (E36) 325ic
81 BMW (E12) 528i
04 Outback
02 Acura TL Type S

chrisshara
First Gear
Posts: 164
Joined: Thu Apr 26, 2012 1:41 pm
Location: Middletown, CT

Re: Intermittently brake pedal goes to the floor while drivi

Post by chrisshara » Tue Mar 15, 2016 4:18 pm

I ordered the vacuum pipe that has the non-return valve inside $22. I couldn't find the part number on the diagrams on parts.subaru.com, but the brake booster diagram at the dealer provided more details.
94 Legacy GT
95 BMW (E36) 325ic
81 BMW (E12) 528i
04 Outback
02 Acura TL Type S

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