Two_Noodles

I have a brake bleeding question,
I have a 1994 4wd SR5. The brake problem started after I changed a rotor and pads (I compressed the front caliper with a C-clamp to get the pads in, then later the brakes acted spongey even though I had not opened any lines).

So I decided to bleed the lines with a vacuum pump. This method didn't work very well, I could get much fluid to come out, and all of it had bubbles.

Now I am trying the open the bleeder valve with a line submerged in brake fluid and pump the brakes method.
When I open the bleeder plugs and pump the brake pedal I only get a tiny bit of fluid coming out- pumping them a dozen times gives me less than an ounce of fluid. The plugs are not clogged ( I can remove them and blow through them).
What should I check next? Is it a bad master cylinder? Could it be air in the master? I don't think I ever ran it dry, but it's possible.

Thanks
Two-Noodles

wyoming9

iTrader: (1)

Some place you either crushed a steel brake line.

Or you have dirt in there blocking the line.



Then again do you get fluid out of the line??

Did you have brake problems other than worn pads and rotors before you started.



I always bleed my brakes with a vacuum bleeder.

GuitarMike

Oh man, there's 1,000 threads on this; even ones where I was stumped, too!

Don't know if you know this, but someone needs to pump the pedal about 3x, then HOLD it down, while you then open the bleeder. You should get a rush of fluid and/or air.
When the flow slows/stops, you close the bleeder, THEN they let up on the pedal. Without that pedal being pre-pumped, not much will happen. You can hear it rush out.

If you are running a tube into a jar of fluid, and you have pressure, you'll see bubbles coming out when you do this even if no fluid's coming out. So you close it, pump again, and open again, til the bubbles are all gone. May take a few times around all the fittings on the truck to get all the air out.
Don't let the MC get more than about 1/2 empty when doing this.

If you're already doing this and get no pressure, you have what Wyoming said...or a bad wheel cylinder or master cylinder, or air in the master cylinder requiring bench bleeding (if it ran totally dry). Try getting some pressure built up before opening the bleeder, I bet that's it.

Two_Noodles

Pumping the brake pedal and then holding it all the way down seems to be helping a bit.
I was holding it halfway down when attempting to use the vacuum bleed method (with a little hand vac pump).
The fluid still seems to be moving really slowly through the lines, but I may be getting there. There is a whole lot of crud in the fluid and it is different colors (green, or milky brown depending on where I'm bleeding it from).

Prior to changing the brake rotor I had had no problems with it. The front end began vibrating while stopping, so I changed the rotor on that side- I think I did it correctly, but the brakes were spongey after that- so I started bleeding them.

wyoming9

iTrader: (1)

Well keep going to all the fluid is nice and clean!!

Sounds like

That could be your problem this was not changed in quite a while.

To much water .

GuitarMike

Yup. Water turns it milky, then brown after a long time. Run a BUNCH of fluid thru it! Don't be shy. And you do need to have someone else pump it, I'd think, if it's this bad. 3 pumps, hold - you open and bleed. Close - then pedal up. Repeat til it's clean, clear, and air-free! Each fitting.

Ideally, you'd bleed them every year, needed or not (few do).

If you opened the brake lines anywhere, you'd have to bleed. If you changed the rotor and pushed the caliper pistons in to get the shoes back in, you'd need to pump the brakes a few times before driving so they pistons come out and auto-adjust to the new pad location. SInce your fluid is crappy, bleed away!
Just don't be shy about generating the pressure you need (maybe 5 pumps, then open). Don't let the MC go below 1/2 way full! Or you'll need to bench bleed....good luck, sounds like you're making progress....

Two_Noodles

Update: I got the front brakes to bleed out just fine.
The back ones are not giving me any fluid coming out after pumping them or with vacuum.

I think I may have a faulty Load Sensing Proportioning and Bypass Valve in the rear. I can bleed both the lines running to the valve (and that is replenished from the master reservoir), but I cannot bleed either rear wheel (no fluid comes out after the first little bit).
Is there a test to see if this valve is good/bad/needs adjustment?
Should I just replace it?
Thanks

Two_Noodles

Yeah, I get fluid from the bleeder valve on the LSPValve (and both input lines), but not from the wheels. I tried adjusting the control arm for the LSPV to run all the way open and it still doesn't let the rear wheel bleeder valves bleed. Rocking the control arm back and forth did not open it up either. I will try a bunch of pressure from the brake system with a bleeder valve 1/2 open to try to force it open, I think the valve is shot though.
Rats, the LSPV is a $150 part too.

Two_Noodles

Update #2. I got fluid to flow through the LSPV and to both of the rear wheel cylinders. It's running nice and clean now. It opened up after adjusting it wide open, moving the control arm back and forth and pumping the brake pedal a bunch. I think the truck has to be running as well. I can't get fluid to flow though the LSPV under vacuum alone, I have to pump the pedal. I will try to bleed the air out of the rear end tomorrow with the pump/pump/hold/open/close and repeat method.
Thanks for the helpful comments!

GuitarMike

I think it's just a matter of pressure, and you may definitely have had crud built up in the LSPV. Shouldn't need the truck running, but if it works....
Glad it's coming along! You might have to try 'em in the driveway, and then bleed them AGAIN, depending on how low you let it go and how much air got in, but you are now very close, i'd say!
Good luck!