Topic: Rear brakes won't bleed. ??

[Yota Up]

85 pickup.

Did some work on the rear gears a while back.
When I did, I disconnected both brake lines at the T on the axle(because the nuts at the wheels were too rusted).

Put it back together and pedal goes to the floor.

Front brakes and LSPV all bleed fine. But both rear wheels don't bleed at all. When you open them, the pedal doesn't move down and barely a drip comes out.

If I disconnect at the T again, I barely get a drip. It's like there is a plug between the LSPV and the T at the axle, or perhaps before the LSPV.

Any ideas?  There are ZERO leaks anywhere. No visible kinks. I've tried bleeding with the LSV arm up and down already.

PS: The rear line is looped up and over from the LSPV before going down to the axle, could that be it?

Picture to show the "loop" and the way the LSV is tucked up under the bobbed bed:


I got a friend that has a spare LSV for me, but do you really think that will solve the problem? After all, it bleeds just fine at the valve.  Maybe one of the lines going "into" the LSV?

I'm stumped, and I've been searching and reading for 5 days now.  I see people replacing everything, MC included.  I'm sure some of you have had this very same problem.  Please let me know what your cure was.

Thanks.

Oh, and which of the 2 lines going into the LSV is the one that feeds the rears?
Maybe if I disconnect it before and after the LSV I can pinpoint where the jam is.

[*ROKTOY*]

I'd change the lspv, and see what happens,

[DTB]

I'd change the lspv, and see what happens,

Maybe try rebuilding it or cleaning it...make sure there arent any clogs in the lines.

[MiniSimp]

Had the same problem, it was a clog, pushed pedal really hard and it cleared, but you may have to just take out your bleeder to see what is clogged.

[weirdtimes_7]

My first thought, apon many other people's first thought's... is that there is a clog in the line. If you have an air compressor, you can dissconect your line and try to blow the clog out, or replace the line.

military_stang

[79coyotefrg]

take both rear bleeders out ,   get in truck  and push down HARD,  if its clogged  it will blow it out

[Yota Up [OP]]

Well, I dig some tests.  Since the LSPV bled fine, I started to disconnect the lines from rear going forward.  Sure enough, of the two lines going INTO the lspv - one of them did not squirt.  I traced it up to the front tire, and still no juice.  Followed it into the master cylinder - and took the brake line out - and just a slow drip like all the rest of the points.

So - it MUST be the master cylinder.  A buddy in town had one for me, so I picked it up.

What an easy job!  Took me like half an hour to swap it out.  Piece of cake all around.  Reconnected everything and ready to test it - oops - my buddy took off with my brake fuild.

So now I get to wait a day until he comes back so we can bleed the whole system and see if it's fixed.

(I wouldn't be surprised.  I heard of another case where a guy replaced everything and it worked for him again.  Perhaps there's something that happens if winter hits and freezing temps can affect any air/dirt in the line that results in screwing up the MC?)

[hatt0710]

Do your self a favor and get rid of the paportion valve on the back frame rail it will just cause you problem in the long run.  Hard lined all my stuff and the brakes have never worked so good!!!

[OOPS]

Brake fluid absorbs water from the atmosphere and over time it gunks things up. That is why it is recommend to flush the system at least every two years, more often in high humidly areas.

[Yota Up [OP]]

Well, I traced that damn "lack of bleed" all the way to the MC.  So the prop valve is alright.  Replaced the M/C and now the rears bleed again.  Finally.  Only took about 15 minutes, piece of cake.  I always had this idea in my head that brakes were a nightmare.  Not so bad.

Brakes are good now - still a bit spongy, but at least they're bleedin' in the rear.  Now I can finish it off and the last air out of there and be set.  Case closed.  Moral - trace it down rather than replace everything blindly. 

[Toymin8r]

Are you using wire braided brake lines for your fexible spots?  If not that will cause the spongy feeling you are experiencing  because the rubber lines will expand from the pressure.

Brake fluid absorbs water from the atmosphere and over time it gunks things up. That is why it is recommend to flush the system at least every two years, more often in high humidly areas.

If you drain all of your brake fluid and switch to DOT5 100% Silicone fluid you will eliminate this problem.  Silicone and water do not mix and does not attract moisture.  This is a PITA though beacuse DOT5 cannot be mixed with DOT3 or DOT4.  You must drain and flush the system completely.   The US Military uses DOT5 in all of their vehicles.

[Yota Up [OP]]

Is the DOT 5 expensive special stuff?  I don't have a lot of access to a lot of consumer goods around here.  Pretty much stuck with what the small town can get.  I guess there's always online.

And yes, I got braided lines for the front and the main drop for the rears.  Cheers.