Air in brake system - '91 Loyale

[Rick]

Hello all,

'91 Loyale 4x4 wagon

I just did a bunch of front-end work that required removing the brake
calipers. After hooking everything back up, I keep getting air in the brake
system at both calipers when I bleed the front brakes. I bleed them until
there's no air, then come back a couple of minutes later and there's air
again.

It seems to me air must be getting in at the calipers because the reservoir
has never run dry. The only things I can think of are: 1) I didn't replace
the sealing washers on the banjo bolts, as suggested by the shop manual; 2)
There are two sealing washers per banjo bolt. I put one on either side of
the banjo bolt assuming that's how it was before, but I don't remember for
sure. Maybe one of these is allowing air to get in?

Any thoughts out there? Thanks in advance.

 

[David & Caroline]

Sounds right with the washers (one washer on either side of the banjo
bolt) - plus, the system would tend to leak fluid out rather than let in air
(since the reservoir is the highest point in the system) - as long as the
washers weren't scored (were still smooth) they should be fine - when you
removed the calipers, you may have gotten air into the master cylinder,
which can be a serious pain to bleed (never done it on a Subaru, but on many
cars you need to remove the master cylinder and bleed it on the bench to get
all the air out.)

 

[Rick]

Hello again,

Ok, here's the deal. I bled all four wheels diagonally and got air at all
four wheels, twice. I haven't bled the master cylinder yet because the bolts
on the brake lines are a major PITA to get loose and, more importantly, the
more I work on this, the more convinced I am that air is getting in.

The thing that has me thinking this is that I have bled enough air out of
the system over the last three days to fill the entire system at least once,
no kidding, not to mention the quart of fluid I have put through it. I can't
imagine that much air could be trapped in there. My understanding of
hydraulic systems is that air can get trapped and compromise the system, but
I have a continuous supply of air bleeding out. At some point the air has to
stop coming out if air is not getting in, even if an air pocket remains
trapped in the system.

So, I'm thinking that maybe it's just a strange coincidence and the master
cylinder has a leak. Any thoughts or, better yet, does anyone know how to
test this? I'm curious to know what other people think.

Thanks - Rick