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Bought a used 99 Outback about a year ago. Daily driven for a few months all was good. One day brake pedal got really soft. Would go to the floor but car would still stop. Changed master cylinder out with one from 97 Outback that was previous daily driver, bled all four corners all was good for about 2 weeks. Pedal goes to floor again with no warning, this time no brakes at all. Now I have no fluid coming out bleeders. Front drivers side just barely dribbles fluid out, front passenger side has nothing. Not made it to rear yet, can't get all four off ground at the same time. Figured no point until i at least get fluid coming out fronts.

Booster seems to be fine. With switch off it has pressure and pedal drops when car is started. However, when switch is off pedal will push almost to floor with some effort. 

When car is running, pumping pedal results in what sounds like air leaking on both the in and out stroke. Sounds like when you breathe in and out with your teeth clinched. But can't find anywhere this could be coming from. Could be normal I don't know.

Could both master cylinders be bad? 

Could ABS pump be bad? I did pull fuse at one point and it made no difference. 

No signs of a leak anywhere that I can see. 

I also, took vacuum hose with check valve off 97 and put on this one with again no difference.

Trying to keep from throwing money at it all willy nilly or doing a lot of double work by stripping parts off 97 to just try. Any help from you experts would be greatly, greatly appreciated.

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Oops missed the hissing sound.

Got tunnel vision there.

O.

Edited by ocei77

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2 hours ago, Phillipt4269 said:

When car is running, pumping pedal results in what sounds like air leaking on both the in and out stroke. Sounds like when you breathe in and out with your teeth clinched. But can't find anywhere this could be coming from. Could be normal I don't know.

The hissing sound is probably the diaphragm in the booster leaking. 

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How's the level in the reservoir? Do you loose fluid?

 

 

Your's sounds like a fluid leak. Any other symptom I can think of would yield a spongy or hard pedal, but still functional. These are somewhat notorious as they get old for rusting out lines above the fuel tank, so look for brake fluid leaking down from that area, usually on the passenger side.

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First time fluid level stayed the same. This last time it had went down just a dab maybe 1/4" if that but no signs of fluid anywhere underneath car. Would this fluid be running off the side of the tank where I can see it, or is just one of those Subaru things you know is there? Also, I read somewhere, on here I think, that a caliper could be letting air escape somehow. Is there any way to test for this leak or a possible leaky caliper. All y'alls assistance and input is greatly appreciated I'm just trying to keep from throwing money at it. Although new calipers wouldn't hurt nothing I guess.

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Remove the master cylinder from the booster and see if there is brake fluid on the back side, it should be dry.

Get plugs to fit the brake line holes in the master cylinder. Remove the lines, put the plugs in and see if you get a pedal back.

Sometimes you can see the fluid churn inside the reservoir when the pedal is pushed if the piston seals are bad. 

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2 hours ago, Phillipt4269 said:

First time fluid level stayed the same. This last time it had went down just a dab maybe 1/4" if that but no signs of fluid anywhere underneath car. Would this fluid be running off the side of the tank where I can see it, or is just one of those Subaru things you know is there? Also, I read somewhere, on here I think, that a caliper could be letting air escape somehow. Is there any way to test for this leak or a possible leaky caliper. All y'alls assistance and input is greatly appreciated I'm just trying to keep from throwing money at it. Although new calipers wouldn't hurt nothing I guess.

Yea, it would eventually be running off. Depending exactly where the leak is, it might take awhile to be visible. But with your symptoms, I was expecting an empty reservoir.

Any leak would leave fluid, and not terribly difficult to see, so I don't think that is your issue.

 

I suppose it's possible to have a catastrophic master failure.

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Sorry for the delay been working and can only work on car on weekends. So today I replaced both front calipers (gut feelin) and bled all four. Still no pedal. I do have fluid coming out all four wheels now just no pressure on the pedal. Thank you again for all your help. Also, no signs of a leak anywhere on the undercarriage. Not at gas tank nor anywhere else. With probably 1000 pumps of the pedal the last 3 weekends One would think I would see fluid somewhere.

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If no external leaks are noted and no drop in reservoir fluid level, Rampage's suggestion that internal master cylinder seals are failing, allowing fluid to pass by and not build pressure seems like a likely culprit.

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2 hours ago, Phillipt4269 said:

With probably 1000 pumps of the pedal the last 3 weekends One would think I would see fluid somewhere.

Yes, and you would have had to add several gallons of fluid to the reservoir.

Plugging the brake line out puts of the master cylinder and pushing the pedal will tell if it is capable of working. If it goes to the floor, then the seals on the pistons are shot.

Auto Parts Stores have what they call a bleeder kit consisting of four plastic plugs. A lot of times they come with a new or reman master cylinder.

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My apologies for the long delay I have been working all the time. Update, replaced front calipers previously mentioned, master cylinder, booster, and abs module off 97 parts car that had good brakes when parked back in spring. Still no pedal. Broke down and bought new master cylinder bench bled it, bled all four wheels, and bled at abs pump. Still not right, does stop and is drivable but not right. 
When first touching pedal it feels like it is going to stop, can feel it in pedal and in car “motion” then pedal continues to collapse, for lack of better words. At this point car does stop but you better not bow up in front of me you will get hit as brakes just lock up when applied hard.

Still no sign of a leak.

Is there a relay to change? Every car I ever had with abs had a relay in the box under the hood this one does not. Is there one somewhere else? Is there a solenoid of sorts that controls everything? Feels like it wants to work but something is happening to the signal being sent when braking.

 

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LINK

Odd, that while I see a relay for the 99 Forester, the above link doesn't show it as a part for the 99 Outback.

Was there a relay on the parts car? Trouble diagnosing when mixing parts from different model years.

You might want to call a dealership and ask them by VIN if there is a relay for your car or if they can send you their parts schematic for the system.

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