Trouble Bleeding Brake Lines

[PossumF250]

I'm nearing the end of the long, slow process of replacing/rebuilding the brakes on my '84 F-250 4x4 and having trouble getting the brakes bled. I am using a Motive Products power bleeder with the 0105 adapter and at first had no trouble getting a steady stream of brake fluid at each bleeder screw, and got it to where I had no air bubbles in the fluid. The brake pedal still felt too soft, so I thought maybe I hadn't bled the master cylinder well enough when I put it back in a couple weeks before this. I took it back out and bench bled it again with a bleeder kit (plastic adapters and clear hoses to recirculate the fluid) instead of the plugs this time. I bled till I wasn't seeing any air bubbles coming out and reinstalled it, then tried to bleed the brakes with the power bleeder again. This time I only could get a little brake fluid to come out at the wheel cylinders, then it would either stop or begin sucking back in. I think I may have had the parking brake on when I started, then took it off (with the truck in gear in a flat spot in the yard, of course). The only other thing different from the first attempt was that I didn't have the rear end up on jack stands, but I don't see how either of those things could have caused it.

My questions are: was I likely on the right track with bleeding the MC again, how can I be sure I've done that properly, and why couldn't I get brake fluid to come out on that second attempt?

Thanks in advance for any information/advice y'all can give!

 

[IDIBRONCO]

This may or may not help. I have a Harbor Freight power brake bleeder. I thought that it was going bad because it would barely pull any brake fluid out. I finally figured out that there was a clog in the suction hose that attaches to the bleeder valves on the vehicle. After I cleared that, it worked fine again. You might try seeing if that hose is clear on your bleeder.

 

[Cubey]

i had to install the MC and bench bleed it with the brake pedal, because it wasn't bench bleeding properly by hand

 

[rreegg]

Regardless of bleeding method don’t forget to adjust/tighten rear drums if the system seems bled but has soft pedal

 

[IDIBOBS]

Adjust rear drums properly. Check for leaks. Then have 1 person sit in cab and 1 person at the bleeder. Open bleeder and Have them push 3 times hold down the pedal and then tighten the screw. Start at the back of each wheel 3-4 times and move forward. Make sure you check your fluid level often. I’ve been doing it this way for 30plus years. Never once had an issue It works just fine on $200,000 cars and on $500 beaters. Even if the master wasn’t bleed enough it will be after doing this.

 

[franklin2]

I would not pump the pedal with the bleeder open. Only when it's shut, and then get them to hold pressure on the pedal while you open the bleeder. Tell your helper to hold the pedal down till you get the bleeder shut again. Then they can lift and pump again. Having a helper work the pedal is the best fool-proof way to bleed them. It is a problem if you are by yourself.

 

[DirtyWood]

I've never had a helper for bleeding brakes and just used the cheap and simple DIY one man brake bleeder:

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This works for me everytime.

 

[PossumF250]

Okay, so I'll check for a clog in the hose - didn't even think of that before. Once I get the brake fluid flowing properly again, if the pedal's still soft after another bleeding, I'll probably try bleeding the MC on the truck and see where that gets me. I am pretty confident that drum adjustment isn't the issue, although it probably was at first. I tightened them up till I could just barely get the wheels to move with both hands and a lot of force - probably too tight, but I can loosen them as needed later.

As a side note, I got the power bleeder because I read about how the brakes on these trucks often can't be fully bled using the old method with a helper at the brake pedal due to the proportioning valve limiting the flow to the front brakes till adequate pressure is built going to the rear brakes. I don't know, but I did like that having the whole system pressurized for an extended time helped with finding and fixing leaks.

 

[franklin2]

As a side note, I got the power bleeder because I read about how the brakes on these trucks often can't be fully bled using the old method with a helper at the brake pedal due to the proportioning valve limiting the flow to the front brakes till adequate pressure is built going to the rear brakes.

That is fake news

 

[DirtyWood]

Those power bleeders have been known to malfunction and spray brake fluid all over nice painted surfaces--not common but certainly possible. I know of one mechanic who was using a power bleeder at work and something "gave" and brake fluid went all over the customer's car requiring a very expensive new paint job.

 

[Nero]

I ended up trading in my plastic constructed mityvac for a metal one, and in the 9 years Ive had it, its never leaked.

 

[DirtyWood]

I ended up trading in my plastic constructed mityvac for a metal one, and in the 9 years Ive had it, its never leaked.

Do you know of a different part or DIY solution for the tiny catch jar on the mityvac? Sometimes it's necessary to suck a lot of fluid through the lines and the itty-bitty catch jar seems to fill up way too fast.

 

[ihc1470]

Unless you have someone filling the master cylinder the itty-bitty catch jar is about the right size to not run the master dry. There is that problem going to something bigger. I made one out of a quart fruit jar, just have to put fittings in to the sealing lid.

 

[Nero]

No I have always used the small jar, I could fill it twice before needing to top off the master cylinder. Kept it easy to keep track.