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Old 10-16-2017, 01:35 PM   #1
mtbiker278
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Member#: 242578
Join Date: Mar 2010
Location: Maryland
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2010 WRX
Spark Silver

Default 2010 WRX Stiff Brake pedal on cold start

Hi All,

I have a 2010 WRX wagon with ~130k on it. Lately on cold start-up I've been noticing that the brake pedal is super stiff. I can still depress it with some effort, but essentially all the reserve vacuum is gone overnight. Upon start up the vacuum comes back and brakes function normally.

After some searching it seems like the culprit could be 1 of 2 things going on. Either I have a bad check-valve in the vacuum line, or the brake booster has a slow leak. With the engine running everything works normally so I'm thinking it's likely not the booster (or at least hoping). The vacuum line in question is supposed to have an embedded check-valve to prevent loss of vacuum if the engine cuts out, or under boost. I'm thinking that either the line is just old and needs to be replaced due to age, or that the check-valve isn't functioning properly (not fully closing, or leaking overnight).

Vacuum line in question

While the part is only $20, is there anything I can do to verify this is indeed the problem before I start buying parts? I've seen a couple other threads elsewhere of Forester XTs having a similar issue, particularly in the cold, and this line is shared across vehicles.

Any help would be appreciated!
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Old 02-12-2020, 11:47 AM   #2
flintexpert
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Hi


Did you ever solve this problem? Having the same issue and the dealer is trying to convince me that it is normal for this car...
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Old 02-12-2020, 12:05 PM   #3
mtbiker278
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Member#: 242578
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Location: Maryland
Vehicle:
2010 WRX
Spark Silver

Default

I eventually pulled the vacuum line and tested if the check valve was working. The line seemed good, but I flushed it out with some kind of cleaner (probably MAF sensor spray). I never replaced the line, and chalked it up to temperature difference between super cold, and running. The effect went away in the summer.

Not exactly helpful, and I'm not sure replacing parts will fix it. Best advise is to keep the e-brake on when starting, and mash the brake pedal before ignition.
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Old 02-12-2020, 12:30 PM   #4
flintexpert
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My 2018 Forester XT developed this issue around 14,000 miles. The reserve vacuum shouldn't bleed off overnight IMO - there must be a leak somewhere, either in the brake booster, the check valve or the line between the check valve and the brake booster.


The dealer is trying to convince me that a hard brake pedal is normal for this car. Well how come it wasn't normal for the first 2 years of ownership?? And this is all in warm weather area that never gets below 68 degrees F. SMH.
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Old 02-12-2020, 04:43 PM   #5
mtbiker278
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Member#: 242578
Join Date: Mar 2010
Location: Maryland
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2010 WRX
Spark Silver

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They should be able to vacuum test the booster with the line. Seems really odd to be happening so soon on such a new car. Sounds like a warranty claim.
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Old 02-13-2020, 06:25 PM   #6
flintexpert
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Yeah well this dealer isn't warranty doing anything to a system that is "functioning normally". Arrghhh. And they are the only game in town.
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