Can't bleed brakes after new cylinders.... (1 Viewer)

[edwjmcgrath]

I just completed replacing all of the rear cylinders and shoes. Needless to say, the brake fluid drained the rear reservoir empty during the process. After I got everything back together, I did a basic adjustment and got ready to bleed as I always have.

I refilled the reservoir, cracked open the right rear speedbleeder and stepped on the brakes and the pedal only goes half way and feels firm. I've tried pumping several times and it still doesn't go to the floor. It feels like there is no air in the system-but of course, it's ALL air. Nothing comes out the bleeder.

I've tried the other wheel, I've tried backing the bleeder out a full turn.

Is there a check valve in the master that could be stuck? Do I need to bench bleed the master? I wouldn't think the master would behave this way if it needed bleeding. What am I missing? Something dumb I hope...

 

[Pin_Head]

Seems strange. There is a lot of air in the system, so you may need to pump more or prime the master first. If you can't get the fluid pumping maybe you have a bad master?

 

[mydogpea]

You mentioned in another thread that one of the old cylinders was leaking rust, Brake lines are very skinny, maybe there could be some rust particles clogging the lines???

 

[Jerry D.]

This happened to me once. I bought two new brake cylinders (non OEM) and swapped out the rear passenger brakes. And like you, when I went to bleed the system, I had a soft peddle and no fluid coming out of the bleed valve(s) on that wheel.

Checked other brakes and got fluid out of bleed valve.

What I finally did was take out the bleed valves of the new cylinders and pushed a small piece of wire into the hole, damn, the hole did not go through. Both were threaded and had bleed valves but neither was drilled through.

Took a small drill bit, drilled them out, completed the brake bleed, happy ever after.

May not be your problem, but it was mine...

Jerry D.

PS: Another time on a 4Runner, replaced the front calipers, had my wife help with the bleeding, she pumped the brake peddle. No fluid at calipers, peddle OK wife said. Opened lines, blew out lines, got wife to help with the bleeding, no fluid at calipers. On the third rebuild of the lines, and another bleed attempt, found that the wife was pumping the clutch peddle all this time. Oh well...

 

[ducktapeguy]

PS: Another time on a 4Runner, replaced the front calipers, had my wife help with the bleeding, she pumped the brake peddle. No fluid at calipers, peddle OK wife said. Opened lines, blew out lines, got wife to help with the bleeding, no fluid at calipers. On the third rebuild of the lines, and another bleed attempt, found that the wife was pumping the clutch peddle all this time. Oh well...

Haha, we must be married to the same person because the same thing happened to me. After 4 hours and a couple of complete teardowns of the entire brake system, at least I can say every single inch of brake line was clear after that incident. That's what pushed me into getting a vacuum bleeder.

 

[edwjmcgrath]

Ok, I have some more data....
First, I double checked and am pretty certain I was pushing the brake pedal and not the clutch..... I got speed bleeders so that I can do it myself.
Second, I tried bleeding the front again. This time the pedal would go to the floor. I got a good solid squirt of fluid every time I pressed the brakes. Within 4 or 5 presses, the bleed tube was full of fluid and there were no more bubbles coming out.
Third, I tried bleeding the rear again. The pedal would only go halfway again and I got a "half hearted" spritzt of fluid out of it each time I pressed the pedal. I did this maybe 20 times on each side. The tube never filled with fluid and I didn't have confidence that I was done bleeding. I took it for a ride and it felt like I had 'brakes' but not BRAKES. I'm pretty sure that the fronts are working and the rears are not. It feels like it always did. Can the master fail so that the front works ok, but the rear does not?

 

[3jvj]

Have you adjusted them out? They can be maxing out the piston, but still not grabbing tight.

 

[3jvj]

Ah, I see you said basic adjust, so I'm assuming "yes", but I'd give it another look to rule that out.

 

[Gumby]

Yes the master can go bad on just one circuit. It's kinda why there is two circuits. In fact, I have seen a master go bad because someone was pumping the brakes all the way to the floor. The corrosion in the areas of the master where the seals don't usually go can tear a seal.

You could also have a stuck low pressure switch. Do a little percussive adjustment on it.

You could also have a bad brake hose to the rear axle. Sometimes a flap of hose comes off on the inside and acts like a little check valve. Try bleeding before the hose. In fact, try bleeding right at the master first. No need to pump. Just open the line a turn and have an assistant step on the peddle. close it before they let up.

 

[edwjmcgrath]

Have you adjusted them out? They can be maxing out the piston, but still not grabbing tight.

Yes, I adjusted the rears until they wouldn't turn and then backed them off 2 clicks each.

More data that I didn't mention....For the last few months, I would notice that the brake lights would stay on. The brake pedal would not return completely unless I manually pulled it up. I even changed the return spring to make it stronger and it would still not return on its own..

I'm thinking that maybe the rear part of the master is gone...