Brake Bleeding Woes- Reverse Bleeding?

"bshappy" (bshappy) 04/16/2019 at 14:24 • Filed to: None

1

18

I replaced the front brakes (soft lines, disks, calipers) on my FJ 40 this past weekend and now I’m having trouble getting good pedal. Its possible some air was introduced into the master when I was fighting with attaching the soft line. I used the 2 person pump/ clear tube into a bottle method and I have no more bubbles coming out of the lines but still no luck with the pedal. I’m not sure why.

I was doing some reading and came accross this:

!!! UNKNOWN CONTENT TYPE !!!

It uses a pump to push fluid through the bleeder back up to the master cylinder . The logic is that air wants to travel up, not down, so in theory this would force whatever air may be in the lines up through the reservoir . It kind of makes sense but review are mixed. Anyone have any experience with this?

Aremmes > bshappy 04/16/2019 at 14:35

2

I dunno, it seems to me that this co uld leave air pockets in the caliper pistons in cases where the banjo bolt sits lower than the bleeder screw.

merged-5876237249235911857-hrw8uc > bshappy 04/16/2019 at 14:35

2

I don’t have any experience with reverse bleeding, but I’m a huge proponent of the motive power bleeder.  Just put the cap on give it a test pump to make sure it holds pressure, release, fill bottle with fluid and pump it back up.  Then just open bleeders one at a time.  Job done.  Worth every penny.  I’ve used mine on at least a dozen different cars over the 4-5 years I’ve had it.  

benjrblant > bshappy 04/16/2019 at 14:36

1

No experience on a vehicle, but this is how most bicycle hydro brakes are bled. My main concern on an FJ40 would be overflowing the master reservoir.

Junkrat aka Rick Sanchez: Fury Road Edition > bshappy 04/16/2019 at 14:44

1

Another vote for the Motive Power Bleeder. I have had mine 11 or 12 years and it has worked flawlessly. It makes the hardest part of bleeding the brakes the jacking up and taking off the tires.

bshappy > benjrblant 04/16/2019 at 14:54

0

I would have to turkey baster out the fluid as it fills the reservoir .

bshappy > merged-5876237249235911857-hrw8uc 04/16/2019 at 14:55

0

I was looking at that as well but would it purge the air if there is air in the master? That’s what I believe is the root of the problem because the bleeders are bleeding clean. 

jminer > bshappy 04/16/2019 at 15:05

0

Bleeding has to be done in 2 steps, master cylinder and the lines.

A master cylinder is usually bench bled before install to get air out of the pistons and such.

On my motorcycles it’s usually bleed the lines then several slow pumps on the master that that’ll work the air out of the cylinder.  Don’t stomp the pedal, that will turn large bubbles into lots of small ones.

Spamfeller Loves Nazi Clicks > bshappy 04/16/2019 at 15:29

1

See, shit like this makes me wish I had no ethics.

Pure. Fucking. Snake. Oil.

If it was so great and so reliable and so much better, why does literally no manufacturer recommend it? Oh, right, because it’s a conspiracy to sell you... absolutely nothing whatsoever. Pay no attention to the century of evidence that it’s bullshit, much less the science and physics.

“Air wants to travel upward”? Gods. What a bunch of pseudo-scientific bullshit that ignores actual brake system layout . I will grant it’s a convenient tool for some niche jobs, but I mean, come the fuck on. “the toughest jobs, like the For Ranger clutch in minutes” - For what Ranger? “No special tools or clips to bleed ABS” - uh, yeah, that’s completely false. “Even ABS” - you can bleed post-pump ABS as-is. You can’t pump bleed with this either.

If you’re still getting sponge, it’s far more likely the master cylinder is just plain shot or you have an installation problem.

Junkrat aka Rick Sanchez: Fury Road Edition > bshappy 04/16/2019 at 15:46

0

I would think so, but I always bench bleed a master no matter what.

bshappy > Spamfeller Loves Nazi Clicks 04/16/2019 at 15:54

0

Its crazy how many polarizing reviews this thing has. I think I’ll give the 2 man method another go. If I can’t get a good pedal I’ll look into the Motive. If that doesn’t work maybe the master is bad? Seems odd that the bakes would work fine then the master would fail after just replacing calipers but its possible. My first thought was a leak as you suggest so I checked every connection and found nothing. Then I topped up the master and marked its level and left it overnight. Checked it in the morning and the fluid level was unchanged so I don’t think I have a leak.

Very frustrating .

merged-5876237249235911857-hrw8uc > bshappy 04/16/2019 at 16:25

0

Yes it will purge all the air out of the system.  It works great.  

just-a-scratch > bshappy 04/16/2019 at 19:37

0

I also have a Motive Products pressure bleeder. It did the job when a vacuum bleeder (cheap hand pump type that was garbage) and the 2 person method only gave me a spongy pedal.

bshappy > just-a-scratch 04/17/2019 at 00:17

0

Interesting. I think I’m sold.

just-a-scratch > bshappy 04/17/2019 at 00:40

1

There are some tricks to using pressure bleeders , like keeping the fluid reservoir full, and making sure you have the correct attachments for the reservoir on your master cylinder. I’ve been doing a lot of brake work in the last 6 months, so this has been a very helpful tool.

Changing master cylinders was the most challenging for brake bleeding. There are just so many ways to get air in the lines and places to leak fluid.

I’m sure there are plenty of other good pressure bleeders out there, but I got the most common brand.

Good luck with your project.

brianbrannon > bshappy 04/17/2019 at 12:23

0

Pushing the pedal to the floor can ruin the seals in the master cylinder if it is old and grooved/full of crud. Reverse bleeding is a scam

bshappy > brianbrannon 04/17/2019 at 14:20

0

Is there a way to test the master to isolate that as a point of failure?

My gut is telling me I still have trapped air and just need to keep bleeding but I don’t want to chase my tail for too long if avoidable. 

brianbrannon > bshappy 04/18/2019 at 12:05

0

Push the brakes to the floor and hold. Open the bleeder, close the bleeder. Lift off brake pedal, repeat. If air and fluid isnt coming out in five tries then the master is probably toast  

RacinBob > bshappy 08/16/2020 at 19:07

0

Here’s a couple of things to try.

1. Fill reservoir and get a hose and a bottle. Crack each bleeder in sequence from closest to furthest and gravity bleed each line an ounce or two. That usually does the trick for me. Stomp on the brakes with engine off and see if you have a hard pedal. If the pedal is not hard, g o through steps 1 - 3 stopping once you get a hard pedal.

1. With a set of old pads in the caliper so the piston is out, crack the bleeder and push the caliper in a bit to burp a bit of fluid back through the bleeder to be sure that there is no air in the caliper. Repeat for each caliper. Pump the brakes after completing each caliper to bring the piston back. If you get a hard pedal you are done.

2. Have someone step brakes while you crack each brake line at the Master Cyl. Observe if you get air, Check to see if pedal goes hard after bleeding each line. If you get a hard pedal you are done.

3. If this doesn’t fix it, Repeat step one but instead crack the lines at master cyl.  

If that doesn’t fix it, look up on the web and see how to really bleed your car on youtube.

For me a good gravity bleed has worked every time. By the way, you cannot judge your brake bleeding by hitting the pedal with the engine running, The vacuum boost is enough to make you think they are spongy when in fact are fine. What you feel is sponge is you are really locked and just flexing calipers and brake lines. I’ve sat in a running race car and convinced that the brakes were not properly bled based on pedal feel in the pits with a running engine. But they were just fine on the track.