05 Legacy 5MT 225K

Wanted to change F rotors to slotted units I had. Done. Reassembled and out of nowhere, no brake pedal!!

The brake lines were not opened and there are no leaks. Wound up replacing both calipers as the bleeder screws broke off.

Bled, still no pedal. It works, but goes all the way down. Seemed like classic master cylinder failure. Replaced master cylinder.

Still no pedal!

All four wheels have been bled, the new master was bench bled before installation.

What next? Bad ABS HU, from out of nowhere?

O.

Did the piston return all the way when you bench bled it.

Only other thing I can think of is to check the length of the push rod from the booster to the new master cylinder. If the piston in the master cylinder does not return far enough it can not take in fluid from the reservoir. Make sure the brake pedal comes up all the way.

Brake lines aren’t ballooning when applying pedal pressure are they? 

Cheers 

Bennie

8 hours ago, Rampage said:

Did the piston return all the way when you bench bled it.

Yes

Only other thing I can think of is to check the length of the push rod from the booster to the new master cylinder.     New master is exact same model If the piston in the master cylinder does not return far enough it can not take in fluid from the reservoir. Make sure the brake pedal comes up all the way.     Yes

 

3 hours ago, el_freddo said:

Brake lines aren’t ballooning when applying pedal pressure are they?  Hard to say. Will have to get another person to see.

What perplexes me is there were zero brake issues before removing calipers to change rotors.

This is not just mushy brakes. They are never hard now and as you maintain pressure the pedal sinks to the floor. No real braking when in motion.

 

O.

I've been using the Motive Products 0090 Power Bleeder Tank for a few years now.  It works well and moves plenty of fluid through the brake system to flush it out without pumping the brakes.

How were the caliper pins?  Free movement?

Rusty rear brakes lines seeping.  

Or bleed them and see if any bubbles come out, but if what you say is true those bubbles didn’t get in there magically.  

What’s the time line?  The car ran fine for the previous 2 years, sat for one day for rotor swap, then lost brake pedal the next day?

1 hour ago, lmdew said:

…..How were the caliper pins?  Free movement?

Will double check one side. These are "new" calipers. Even with sticking calipers (have had this before) the pedal s firm, just not stopping very well.

Here the feel is gone and goes to the floor.

55 minutes ago, idosubaru said:

Rusty rear brakes lines seeping.   Will check closer today. When bleeding, fluid came out with good pressure and very few bubbles which I assumed were from the MC exchange. Fluid level doesn't change.

Or bleed them and see if any bubbles come out, but if what you say is true those bubbles didn’t get in there magically.  

What’s the time line?  The car ran fine for the previous 2 years, sat for one day for rotor swap, then lost brake pedal the next day?

Bought this as a project car last year. Wanted a 5mt wagon of 4th gen (best styling IMO). Replaced engine. Been running for 6months as I worked out the little issues. Brakes was never one of them. Was sitting for @ 6mos before I bought it.

O.

 

Edited October 15, 20196 yr by ocei77

Pardon the dumb question but since we only have the internet, how much fluid did you use to bleed?  

They can take a lot of fluid, like 64 ounces, to get all the air out when the system is significantly exposed to air.

That still doesn’t explain the original loss of pedal which sounds like rear rust.  The rust can be layered and sort of soak and deep rather than spray and drip. And it can be on top of the gas tank, all this can make initial leaks hard to find.  

The plan is to check those rear lines closely today.

I did use about 50 oz in my fill of new mc and bleed of lines until new fluid appeared.

Will advise.

O.

3 hours ago, ocei77 said:

as you maintain pressure the pedal sinks to the floor.

If there is a leak the fluid level will drop.

If the fluid level does not drop, the master cylinder is bad. I have seen a few new and reman ones that were bad.

This "could" have happened to the original master cylinder. During normal use the piston will only travel 1/4 to 1/2 of an inch and you have a full petal. The seals are working in that area for years. When initially pumping the brake pedal, if you push it to the floor the piston seals are moving into an area that could be rusty or coated with crud and that would mess up the seals. If they leak the fluid seeps past them and goes into the reservoir.

31 minutes ago, Rampage said:

If there is a leak the fluid level will drop.

If the fluid level does not drop, the master cylinder is bad. I have seen a few new and reman ones that were bad.

This "could" have happened to the original master cylinder. During normal use the piston will only travel 1/4 to 1/2 of an inch and you have a full petal. The seals are working in that area for years. When initially pumping the brake pedal, if you push it to the floor the piston seals are moving into an area that could be rusty or coated with crud and that would mess up the seals. If they leak the fluid seeps past them and goes into the reservoir.

The MC fluid level is a good easy check but isn’t always a good indicator of some initial rust leaks. The fluid can leak, not through a hole, but through the meandering layers of rust and isn’t a traditional “leak”. I’ve seen the rusty lines just darken but no actual fluid, no running or dripping, it’s just wetting the rust. It’ll leak “just enough” for the pedal to slowly go down but not enough to notice fluid level at first. This is further complicated if it’s rear lines running above something and not visible.  

Subaru MC failure is rare, so rare its unlikely. First one was probably fine. Every guessed Subaru MC replacement I’ve ever seen ended up not being the issue (including my own guesses!). I’ve only seen one Subaru failure, it leaked between the MC and firewall but caused no issues except flaming paint because it was like that for like 10,000+ miles. 

Edited October 15, 20196 yr by idosubaru

8 minutes ago, idosubaru said:

Subaru MC failure is rare,

Our 95 RHD has almost 469,000 miles and the mc is original. One time I thought it was going bad, but (as you stated earlier) it was the brake line over the gas tank. I rerouted it under the rear seat. There are rubber plugs on each side of the floor.

No visible wet spots.

Will run new lines to proportioning valve and go from there.

Thanks to everyone for their suggestions and help.

Will advise. Have to figure out line size and get a flaring tool.

O.