Topic: Proportioning valve bleeds, rear brakes don't

[HeroClass]

New calipers, new pads, new hard lines to the calipers.  Brakes well, but pulls to the right so I went to bleed everything and can't get any fluid out of the rear brakes.  I get SOME fluid with air from the 2 front brakes and the proportioning valve.  I know fluid is getting to the proportioning valve, but not the rear brakes so does that mean the valve is bad?

[HeroClass [OP]]

Sorry, I should have specified.  This is a 1985 4runner SR5 22re.

[H8PVMNT]

Let it sit and gravity bleed with the rear bleeders cracked open for a good long while until you get fluid. Then just keep on bleeding.  I've have it take for ever.  Maybe someone else has a better idea.

I have had one bad proportioning valve but the systems with the multiple brake lines going to the rear like that just take a lot of effort.

[Prismo]

I have had the bleeder screws in the rear brake cylinders plugged with rust & dirt a few times. Pull the bleeder screw & see if it is clogged. If so a bit of welding wire can usually be used to clean the crap out. 

[79coyotefrg]

No,  remove the lever thing from the rear axle and tie it up to the frame as high as you can.  This will open the proportioning valve so you get full pressure to the rear brakes.
Bleed the rear brakes then and you should get all the air out

you might even keep it up if you are running large tires to help stop.   A good rule of thumb it to raise the lever from the rear axle as high as the lift you have.

[OVRAROK]

I removed. Right near the passenger front wheelwell, Ended up putting a 2 way, instead of a 3way.  Installed proportioning valve right at the master cylinder.

[Ritchie]

... something like this Hero. Once you dial it in, the brakes are awesome.

[HeroClass [OP]]

First of all, thanks for all the replies!  These forums are always my first stop for advice and they never disappoint!

H8PVMNT: I've spent countless hours for the past 4 weekends trying to get these things to bleed, including gravity and vacuum, and I get nothing.  No bubbles, nada, so I don't think it's a time issue. 

Prismo:  I replaced the rear bleeder screws when I installed the new front calipers.  Checked them a few times since to make sure they aren't clogging from gunk, rust, etc.

79coyotefrg:  I have not tried this yet and it never occurred to me that the lift could affect it.  I'm green to a lot of this mechanic stuff, so I'm learning as I go.  I will definitely give this a shot.  It's currently a 3" lift with tiny little 235s lol. 

OVRAROK/Ritchie:  Eventually the plan will be to either bypass/remove completely or relocate, along with a new master cylinder, but at the moment I'm going with functional fixes.  Upgrades will definitely come later.

Thank you again everyone!

[OOPS]

Start at the source, take the rear brake line off the MC and push the pedal to see if fluid is coming out there!! Work back from there making sure the brake lines are not clogged somewhere. If you are still running the rubber line it could look but be broken down inside. I had a case on a motorcycle where it sat so long the little hole in the MC was so clogged up it did not allow fluid to go to the wheel cylinder when the pedal was pushed.


Brake fluid gets weird if it has been in the system to long. That is why it is recommend to flush the system every two years and more often in high humidity areas!!

[Jimkola]

Good advice here, and especially Oops and Coyote.
If the vehicle was raised, but the proportioning valve lever was never adjusted to accommodate the new height that could cause your issue. I think there’s about two inches to play with on  threaded rod at the diff.
Debris in the system from the brake hose is rare, but possible. I never liked, or used, those brake vise grip pliers that pinched the hoses. They definitely could cause internal breakdown of the interior hose lining. What a terrible shortcut.
FWIW:as mentioned, there is a procedure in the factory manual for adjusting the proportioning valve. BITD we weren’t fond of  it. The results were never as “dialed” as we would have liked. And if the truck is anything other than bone stock I’m not sure it’s worth it. But I guess it won’t hurt to try.
Funny, one of my friends who worked on the Tech Assist hotline Dept at TMS for many years stopped by last week.  We somehow got on the subject of the proportioning valve adj procedure. Toyota’s diagnostic approach was still fairly rudimentary back then.

On a more positive note, my friend gave me a TMS internal document from 1992 that is 44 pages of bearing numbers. It gives the Toyota part number along with the manufacturer number for cross referencing. So if you need koyo, Naiche, etc numbers send me a message.
Cheers,
Jim