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Old 05-24-2018, 06:44 AM   #1
some dude
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Join Date: Nov 2005
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06 WRX
CGM

Default Brake light comes on with boost off with a hard braking

Stock brakes 2006 wrx tr. I just rebuilt my rear calipers and put new pads and rotors on the rear. No problem before this, and didn't touch the fronts.

When I first drive, brake light comes on quickly.
If I brake moderately hard from 45-15 or 55-30 the brake light goes out.

But as soon as I get around half throttle and get soon boost going, the brake light comes back on.

I can easily clear it and bring it back over and over as described.

Does anyone know what's going on?
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Old 05-24-2018, 06:58 AM   #2
some dude
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Default

Quote:
Originally Posted by some dude View Post
Stock brakes 2006 wrx tr. I just rebuilt my rear calipers and put new pads and rotors on the rear. No problem before this, and didn't touch the fronts.

When I first drive, brake light comes on quickly.
If I brake moderately hard from 45-15 or 55-30 the brake light goes out.

But as soon as I get around half throttle and get soon boost going, the brake light comes back on.

I can easily clear it and bring it back over and over as described.

Does anyone know what's going on?
Ok, quick update.

I drive the car 30 miles this morning, mostly highway. The car sat for 15 minutes and I got back in and drove.

No brake light, even under boost.

It had gone away ( the ability to trigger the brake light) before, after driving a while.

It's most present and able to trigger if the car has been sitting for hours and hours.
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Old 05-24-2018, 09:31 AM   #3
Charlie-III
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Location: USA, North NJ, 07456
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1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

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Check brake fluid level. If it's near the lower limit, cornering, hard braking, hard accel sloshes the fluid around in the master cylinder.
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Old 05-25-2018, 10:40 AM   #4
some dude
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It's a little low, I will top it off and report back. Thanks
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Old 05-25-2018, 01:04 PM   #5
Charlie-III
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1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

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Quote:
Originally Posted by some dude View Post
It's a little low, I will top it off and report back. Thanks
Add some fluid.....don't top it off.
Why?
In most vehicles, unless you are leaking fluid, when you get near the lower limit for a brake master cylinder, something is almost worn out. Usually pads, could be pads and rotors.
When you replace parts, master reservoir should be about full again.
Good time for a fluid change.

Get your reservoir to a bit (1/8"?) above the lower limit, see if the brake lite on the dash stays dark. Go from there.
The E-brake switch can also trip the same light.
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Old 05-26-2018, 08:42 PM   #6
some dude
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Well I added a little fluid because it was below the full mark. The light went off and hasn't come back.

Thanks a ton!
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Old 05-27-2018, 09:37 AM   #7
Charlie-III
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Silver Sleeper BK, 5MT

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Glad that was it.
Thanks for closing it out.
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Old 05-27-2018, 09:41 AM   #8
Elbert Bass
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Just to clarify - you rebuilt your rear calipers?
Did you bleed the brake fluid afterwards?
Just want to be sure you got all the air out for your safety. When you bleed brakes, (especially dry calipers and open lines) you should have to add fluid at least once or twice to the master cylinder unless you use a refill reservoir.
I am concerned because your post gives the impression you haven't checked your fluid.
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Old 05-28-2018, 11:22 AM   #9
some dude
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06 WRX
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Yeah, I did bleed the rear brakes after I was all done. Thanks for checking.

The car feels normal, no bad lights.
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