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2014 Outback 2.5L
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Discussion Starter · #1 ·
So as the title says I get air in the brake lines every 6 months or so. We live on a dirt road so the other day when the brake pedal went soft I got going about 25MPH on the dirt and slammed on the brakes to actuate the ABS and the bakes pedal immediately felt solid again. I popped the cap off the master cylinder and there was a big air bubble floating in there. After looking closely at the ABS actuator (I'm guessing that what the ABS module with all the lines in and out is called) I noticed the top of the module where the 4 lines go in there was evidence of some moisture, I'd describe it as "sweating". I probably wouldn't even have noticed if I wasn't specifically looking for a leak on the ABS module and the engine wasn't covered in dust from the dirt road.


I put a wrench on the 4 lines and they're all tight, as tight as I dare to wrench on them, I've cracked enough hydraulic lines in my day to be a little gun shy. Has anyone else had this issue before and if so any ideas how to remedy it.


Thanks fellas
 

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Discussion Starter · #7 ·
I'll check out the vacuum line when the car gets back this afternoon and see if there's a check valve. Although pumping the brakes hasn't helped before (I think this has happened three times now) I'll replace it before I go tearing into the hydraulics.The fact that there's a little moisture on the ABS module led me down that road, then the bubble floating in the master cylinder after I actuate the ABS and the pedal firming up kinda kept me going that way.


Thanks for the help and I'll keep y'all posted.
 

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Discussion Starter · #8 ·
Here's some pics, I don't see a check valve in-line but there is either a filter or check valve behind the metal bracket attached to the booster. Is this the check valve you're talking about?
 

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2014 Outback 2.5L
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11 Posts
Discussion Starter · #10 ·
Not really sure if it's brake fluid, it's really hard to tell if it's even fluid at all or if it's in any way related. know there shouldn't be any fluid on the outside of the module though. I may be talking myself into something so I can explain the problem. I'm gonna try the check valve and see what happens. The problem is it only happens very so often (it's happened three times in 4 years) it's hard to replicate let alone diagnose the issue.

I still have a hard time wrapping my head around why after I slam on the brakes to get the ABS to activate there's an air bubble floating in the resevoir. I can see the pulsing of the ABS breaking the check valve loose though. We shall see.
 

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Discussion Starter · #13 ·
idosubaru: How do you go about activating the ABS module without stepping on the pedal? Do you apply 12V somewhere on the module?


Texan you're correct. 3 times in the last 4 years the brake pedal will basically sink to almost the floor. In the past I would bleed the brakes and all would be fine for like 9 months to a year. This last time, about a week ago, I took the car out on the dirt road we live on and slammed on the brakes. I could feel the ABS pulsing and the pedal immediately firmed up back to normal. I got out of the car and took the lid off the master cylinder and saw an air bubble floating in the fluid, that led me down the road of something leaking, or not being tight anyway.
 
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