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Soft Brake Pedal
#1
Posted 20 December 2012 - 06:00 PM
#2
Posted 20 December 2012 - 06:04 PM
#3
Posted 20 December 2012 - 07:58 PM
The are specs for testing the booster in the FSM I think. Basically check the amount of vacuum at the booster by putting a T adapter in the hose past the check valve. It should be the same as at the engine. Turn the engine off and vacuum should stay the same. If vacuum decreases the booster or check valve could be leaking.
With the engine running pump the pedal a few times then release. Turn the engine off. Push the pedal hard down and fully release at least 4 times until the pedal doesn't sink anymore, then hold. While still holding start the engine, the pedal should sink about 1-2". Pretty sure the spec for these cars is in the FSM.
If it passes that test, and is getting the proper source vacuum and holding it after the engine is turned off, the booster is good.
#4
Posted 20 December 2012 - 08:01 PM
#5
Posted 20 December 2012 - 09:38 PM
There is a valve somewhere in the vacuum line I think - maybe that is wonky? They freeze on some folks every winter and cause issues...I forget what.
Subaru master cylinder failure is very rare.....
On other cars folks would say one of your flexible brake lines at the wheel is failing and "expanding" internally - ballooning. Expands to a point then firms up....repeat when it contracts. They can also collapse. I've replace those hoses on other makes but never seen or heard of one failing on a Subaru. It would be one of the 4 flexible brake line hoses at each knuckle assembly.
I have seen rockauto have some crazy cheap brake hoses before....just cross reference the part number and make sure it's the right one.
#6
Posted 20 December 2012 - 09:46 PM
If a wheel bearing is loose the first time you hit the brakes the caliper piston has to move farther to pull everything tight again and then when you hit them again everything is in place so the pedal is normal.
I've seen it before. There bearings don't always make noise when they are bad, and Subarus are pretty easy to bleed the brakes on without much trouble.
#7
Posted 20 December 2012 - 10:26 PM
#8
Posted 20 December 2012 - 10:32 PM
I would assume you probably would have noticed this since you've done all the brakes, but make sure non of the wheel bearings are loose.
If a wheel bearing is loose the first time you hit the brakes the caliper piston has to move farther to pull everything tight again and then when you hit them again everything is in place so the pedal is normal.
This isnt a one time issue, when you first start driving it, it happens every time you hit the brakes. It doesnt matter if it is every 50 feet, or every 200 miles, each time you hit the brakes, it always acts the same. I have checked wheel bearing, and all the front end components because it had a vibration we finally traced to a bad wheel, so i know nothing is wrong there. The only things i can think of it could possibly be, are the front rotors somehow causing it, or either a bad booster, master cylinder, or the front caliper mounts somehow screwed up from being rusted from sitting. I have just spent so much time on these brakes, and replaced so many parts, im starting to think it is just jinxed, so i figured before i messed with it again, i would see what the people on here had for ideas.
#9
Posted 20 December 2012 - 10:37 PM
There is a valve somewhere in the vacuum line I think - maybe that is wonky? They freeze on some folks every winter and cause issues...I forget what.
Thre is a valve in which vacuume line, the one to the booster? Mine is just a solid rubber hose from the intake to the booster, on both of my 99 legacy's.
#10
Posted 20 December 2012 - 10:47 PM
#11
Posted 20 December 2012 - 10:51 PM
#12
Posted 20 December 2012 - 10:54 PM
I had a similar problem for the longest time. It took at least 3 months but the master cylinder went.
That is one of the things im leaning towards, mainly because even though i hear all the time they rarely fail, the car sat for quite awhile, and who knows what the P.O. did when they had the car, or even if the brakes were one of the issues he parked it for, since after i bought it, i found out he isnt exactly the honest type at all, i just dont want to spend the time and the money to do it, and have that not be it. The thing that sucks is, my outback's front brakes are different than the legacy's, so i cant just swap the mounts and rotors from one to the other and see if that changes anything.
#13
Posted 20 December 2012 - 11:21 PM
#14
Posted 21 December 2012 - 12:07 AM
Thre is a valve in which vacuume line, the one to the booster? Mine is just a solid rubber hose from the intake to the booster, on both of my 99 legacy's.
There is a restrictor port in the booster hose something like midway. It's inside the hose, just looks like a little bulge in the hose about 1/2" long.
Id have to go with a bad master cylinder if you're sure you got all the air out of the lines. Brake fluid collects water, any moisture that might have got in the system while it was sitting for that long could have certainly caused the master to rust which would chew up the seals inside it.
#15
Posted 22 December 2012 - 02:34 AM
#16
Posted 22 December 2012 - 11:14 AM
#17
Posted 22 December 2012 - 05:26 PM
#18
Posted 22 December 2012 - 10:50 PM
#19
Posted 22 December 2012 - 10:53 PM
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