Lost almost all brake pressure

[tornichoe]

After completing the brake rotor, pad and fluid flush work on the 15 legacy, I did the pads and fluid flush on the 16 outback; exact same process. At the end of it I have no brake function. When I push it all the way down it catches a little. Assuming it's a master/slave cylinder that was about to go bust, went out in the flushing process..

 

Will be taking it to the dealer later today or tomorrow, but was wondering if there was something that I missed looking at. All bleeder valves are tight and no leaks there. Don't see any other leaks anywhere obvious.

Edited November 18, 2019 by tornichoe

[YeuEmMaiMai]

get in car

start it

pump the brake pedal until it becomes hard

add fluid to master cylinder

go around remove each wheel and use a hand vacuum pump to re-bleed each caliper until no more bubbles, replace wheel, repeat for each caliper and add fluid between each one to the master cylinder.

 

 

you can also use the hose in a coke bottle method if you don't have a hand pump.

Edited November 18, 2019 by YeuEmMaiMai

[tornichoe]

get in car

start it

pump the brake pedal until it becomes hard

add fluid to master cylinder

Tried this yesterday and didn't help.

 

go around remove each wheel and use a hand vacuum pump to re-bleed each caliper until no more bubbles, replace wheel, repeat for each caliper and add fluid between each one to the master cylinder.

you can also use the hose in a coke bottle method if you don't have a hand pump.

 

Used the same method to bleed yesterday and the added the same amount of fluid I bled (refilling the reservoir after bleeding each caliper). The reservoir is above the max line

 

Will try pumping brakes again and see if it helps. Got an appointment with Subaru this evening either way. It's the wife's car so not taking chances..

[YeuEmMaiMai]

remove MC and bench bleed it cause it is the only thing left...

[ammcinnis]

Used the same method to bleed yesterday and the added the same amount of fluid I bled (refilling the reservoir after bleeding each caliper). The reservoir is above the max line ...

If the fluid level in the reservoir dropped below minimum at any time while bleeding, you probably have air in the system ... which is consistent with the symptoms you report. Trapped air can be very difficult to remove once it enters the system. Bench bleeding the master cylinder ... may indeed be required. Your dealer should know how to do it properly.

Edited November 20, 2019 by ammcinnis

[tornichoe]

If the fluid level in the reservoir dropped below minimum at any time while bleeding, you probably have air in the system ... which is consistent with the symptoms you report. Trapped air can be very difficult to remove once it enters the system. Bench bleeding the master cylinder and/or the ABS/VDC valve assembly may indeed be required. Your dealer should know how to do it properly.

 

Thanks!

 

While I can't guarantee this didn't happen, I did take precautions to fill the reservoir every 5-7 pumps or the brake pedal. May be I got lucky when I bled the legacy and the same could have happened there. Don't have the confidence to take the master out and mess around; probably don't have all the tools either...

Will leave it to the dealer for now, can't afford being a car down during the week..

[YeuEmMaiMai]

If the fluid level in the reservoir dropped below minimum at any time while bleeding, you probably have air in the system ... which is consistent with the symptoms you report. Trapped air can be very difficult to remove once it enters the system. Bench bleeding the master cylinder and/or the ABS/VDC valve assembly may indeed be required. Your dealer should know how to do it properly.

 

 

if I am not mistaken the ABS module self bleeds on newer Subaru (not sure don't hold me to it) ...on older cars you could get it to do it by

 

 

1. turn ignition off

 

2. connect diagnostic connector under dash

3. Turn ignition to ON, do not start engine.

4. As soon as the ABS warning light goes off, depress brake pedal and hold it.

5. When ABS pump has finished cycling, turn ignition OFF.

[ammcinnis]

if I am not mistaken the ABS module self bleeds on newer Subaru (not sure don't hold me to it) ...on older cars you could get it to do it by ...

That appears to be correct. I just checked the 2015 Factory Service Manual, and it doesn't specify any special procedure for bleeding the ABS/VDC hydraulic control unit. However, the FSM states that bleeding the master cylinder (in the car) is required if the fluid reservoir is allowed to empty.

Edited November 20, 2019 by ammcinnis

[tornichoe]

Dealer confirmed that there was "a lot" of air in the system. They bled the system and all is good again

 

Guess I got lucky when I bled the Legacy..