Brakes bleeding only half system.

[Mustakrakesh]

So I just replaced my rotors and pads. Seeing as both my rotors had cracks in them making it terribly hard to stop the car.

And I figured while I was at it I'd replace the black brake fluid so I let the system drain overnight and was hoping to gravity bleed in the morning.

To my suprise only half of the system wants to bleed,

 

EDIT: Front left, and rear right are dry as a bone.

          Front right, and rear left are full of fluid no air.

 

So basically I tried blowing air through the "clogged" system (with a bicycle pump lol)

I can see air bubbles coming up at the reservoir! so its not clogged, but no fluid comes through.

 

Before I buy a new master cylinder I'd like to know if anyone else has had a similar problem, and maybe theres a fix?

 

Been at it for over two hours now, I guess I'm not taking her out just yet!

Edited July 19, 2013 by Mustakrakesh

[Mykeys Toy]

If it is bone dry. Start tracing the line for that part of the car..right front and left rear are ( for lack of better terminology ) on the same circuit.  Look for pin holes and check all connections to make sure they are tight..Double check the soft lines..It may still be the master or could be an issue with HH if so equipped.  I do not think so though.  year and type of car may get you a better response from others that know more.

 

Mike

[Mustakrakesh]

Its a 1992 Loyale 4WD with HH I believe. I unscrewed the line for left front brake at the master cylinder and it's not coming from the master either.
So I'm assuming that its my master, when I put some air through and try and push some wire through (was hoping to clear some debris, it was probably a bad idea) some fluid comes out but after a couple seconds or so it stops. So I don't know... It works for a bit then doesn't I can't figure it out. Don't wanna sound like I'm giving up, simply all the information I've looked up doesn't mention one system working and the other completely dry. Maybe I didn't look hard enough I don't know.

[MilesFox]

YOu may need to 'bench bleed' the MC f it ran dry. This is easy to do if you remove the line and place your finger over the hole while someone pumps. There is no need to remove the unit unless you are replacing it.

 

This is a dual diagonal brake system. I assume you know how to do that.

 

I find it helps to bleed out the rear brakes if you depress the clutch pedal while pumping the brake to move the fluid through the rears.

Edited July 20, 2013 by MilesFox

[Mustakrakesh]

So I tired again today, another 2 hours with no results.

Tried with the finger over the MC, with the line off, Built up pressure but after the lines were attached all pressure was gone and I was back in the same spot.

Nothing but air comes through, and the worst part is that there is pressure, but no fluid.

 

When you "bench bleed" are you supposed to cover both lines for front and rear? (on that system FL and RR) because I was just covering the line to the front left caliper. The line to the rear right was attached to MC while I was doing it.

 

I know I must be doing something wrong,

Is it possible for an MC to only put out fluid for half the system (FR and RL)? and the rest is broken internally?

 

Thanks for any and all help :/

-Martin

[idosubaru]

Your MC is fine.  You mention no brake issues and Subaru MC's never fail. It's so rare that a misdiagnosis is more likely than failure.

 

*** What is gravity bleeding?

 

get another person and do it the easy way in a few minutes - pump the brake pedal.

 

or get some air hose like for an aquarium (take a bleeder screw with you as there are different sizes - fronts can be larger than backs i believe depending on model/year) - run it over the bleeder screw nipple and loop it upwards so that fluid/air bubbles don't go back into the screw when yo'ure done pumping.  run the end of the hose in a bucket.

 

the slower way to do it by yourself is to pump the brake pedal a few times, bleed a tiny amount, pump and build up pressure and bleed, over and over.  pumping will build up enough pressure to bleed a tiny amount at a time if you're a masochist and absolutely refuse to get a helper to make it an easy job.

 

there's a couple varieties of pumps that you can attach to the brake master cylinder to push fluid through from that way too - Motive Bleeder or something, i bought one years ago, forget the name.

 

quite a few options to push fluid through.

 

if you're still quesitoning - fill the MC and pump the brake pedal - does the same amount of fluid come out of the bleeder screw on each side?

if so then everything is working properly.

 

a collapsed brake hose prevents fluid flow whereby the rubber hose constricts internally keeping fluid from moving by anything but hydraulic pressure (brake pedal but nothing else).  BUT - failure of this type is extremely rare in a Subaru, i've never seen it in a Subaru.

 

There is also a proportioning valve, i'm not sure how they work but maybe that's putting a kink in the works in terms of the way it directs fluid flow...?

[Caboobaroo]

The hill holder needs to be operated while the brakes are being bled if I'm remembering correctly.

[Mustakrakesh]

The problem could have been two things,

One: I let the master go dry.

Two: I had a pinhole somewhere near the rear right wheel.

 

I tried to remove the piece of line at the rear wheel and it snapped on me,

While I was making a new line I decided to pump fluid from the back to the master using a pump for oil in lower units on motorboats.

After I put the new line on everything worked as it should have.

 

 So hooray for me, and thanks to everyone for helpful advice.

Honestly without y'all I would be waiting on a new master cylinder.

[Gloyale]

nevermind

Edited July 25, 2013 by Gloyale

[idosubaru]

well done not throwing a master cylinder at it.  most 1980's subaru's are running around with original master cylinders in them, they simply are not failure items.

you sir are correct, it was probably bleeding off just enough to not bleed properly but not leaking enough to blatantly show itself.

either way you got it, good deal.

[Uberoo]

well done not throwing a master cylinder at it.  most 1980's subaru's are running around with original master cylinders in them, they simply are not failure items.

you sir are correct, it was probably bleeding off just enough to not bleed properly but not leaking enough to blatantly show itself.

either way you got it, good deal.

I beg to differ the seals just like any other thing do get hard and not work anymore.Recently I took mine apart and flexed the seals and put it back together and it worked better.Then I got a legacy MC..