air in brake lines

[dmjlambert]

Hi folks. My truck is a 69 CST/10 with manual drum brakes. The brakes have been working just fine since I had a friend help me with getting them going. As of that time about 2 years ago we put new cylinders on each wheel, new master cylinder, new shoes, new spring kit, and determined the drums looked fine so we reused those. The brake lines and hoses are in good condition and the system has no leaks. I have neglected to check the fluid level in the brakes, and I let it get low. I noticed the brake on first press when coming to a stop felt different, it was traveling closer to the floor. So I checked and topped off the fluid, but I believe I let it get too low and put some air in the system.

The brakes stop the truck fine, but I am concerned about the feel and about the pedal travel. When I am driving up to a stop sign, if I press the brakes, they go down too far, I think it is about and inch from the floor, and the truck stops OK. I can just tell there is a different feel to it. If I go again and stop some time later, and press the brake pedal, it goes to within an inch of the floor, and if I lift up my foot while coming up to the stop sign and press the brake pedal again, it goes down about an inch higher and feels more like the normal braking position. After coming to a stop, if I maintain pressure on the pedal, it does not sink any further towards the floor.

I am thinking these conditions point to air in the brake lines. I bled the heck out of the system. I used a one-man bleeder, which is a little bottle held with a magnet to something higher than the bleed port, and I pumped the brakes and emptied the bottle multiple times and kept filling the master cylinder with fresh new fluid. I don't think it is likely I would have left any air in the system, I think I know what I'm doing, but it still behaves the same way, so maybe I am missing something. The driver side rear is the longest running line so I started there, and then did passenger rear, then passenger front, then driver front. I have pumped the brakes enough to fill the little bleeder tool bottle several times after seeing the last bubbles go through the tubing, just for safe measure.

Each time I had it bled i took it for a test drive and found the same conditions. I repeated the bleeding a couple times on the 4 wheels, and ended up using about a quart of O'Reilly Dot 3 fluid, which is the same stuff we used when we filled the system the first time.

Do you guys think it is still likely I have air in the system? I am thinking the symptom says so.

I'm going to end up re-doing the system with new braided hose to replace the old hoses, and new drums, shoes, etc. because at the time my friend was helping me he knew more than me and we did not turn the drums, and put the long shoes in the wrong positions, and probably other minor errors, so I want to re-do it because the thought of some of the stuff I have since learned we should have done more correctly is bothering me. I may just replace the master cylinder again if I can't figure out what is up with my failure to properly bleed. And I'm going to put a reminder in my phone to check the darned fluid level and not neglect this thing again. I estimate I have 8000 miles over the last couple of years since getting it going, but it is a guess since my odometer doesn't work.

[Steeveedee]

Make sure that you have them adjusted properly before you go to too much trouble. Also, make sure you put the adjusters back on the proper sides. Replacing the flex lines is a good idea. Take your drums to a shop and have them mic'd. You only need to replace them if they are worn enough.

[RichardJ]

>> put the long shoes in the wrong positions, and probably other minor errors, so I want to re-do it<<

Sounds like the shoes are not adjusted. The self adjusters may not be connected properly. Have you tried adjusting them by backing up and applying the brakes? You don't have to stomp on the brakes or come to a complete stop. Apply firm pressure multiple times while backing and see if that helps.

[87Skier]

I don't think you have air in your lines if you properly bled your brakes. However, some other things can mimic air trapped in the system:

Rear drums out of adjustment
Old rubber flex hose that swells under use
Brake bleeders installed below the level of the brake line (usually only on disc setups)

[Stocker]

Originally Posted by dmjlambert

The brake lines and hoses are in good condition and the system has no leaks. I have neglected to check the fluid level in the brakes, and I let it get low.

If the system has no leaks, how did the fluid level get low? Is it possible there is a hidden leak somewhere that you haven't seen yet? Maybe leaks only when driving, but not in your garage. That might also help explain the spongy feel to the brake pedal. Kinda grasping at straws here, just hate to see you replacing your new parts with more new parts. As others have said, double-check the adjusters again. Make sure they are clean & operational -- a bit of antiseize on the threads will help keep them working.

[randy500]

The brake shoes are out of adjustment.

[LockDoc]

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I agree with Randy....

On the drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel/drum just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear when adjusting them.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly.

LockDoc

[Rich69shortfleet]

Originally Posted by LockDoc

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I agree with Randy....

On the drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel/drum just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear when adjusting them.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly.

LockDoc

With drum brakes I just adjust them so I can just slip on the drums and just do some firm stops while backing up and let them adjust themselves. You don't have to back up at 80 miles an hour and stomp the pedal, just a few moderately firm stops from 5-10 miles an hour will do it. This will also tell you pretty quick if you installed the adjusters correctly. If they don't adjust, you did something wrong. But then, that's why I only ever do one wheel at a time and either reuse my adjuster or compare the new one to the one I'm taking off to make sure I'm using the correct one. Also, by doing only one wheel at a time, you can still use the other side as a reference if you temporarily forget which spring goes where or how things are supposed to fit together. Taking a picture before you start is also helpful sometimes, assuming the previous brake job wasn't done wrong!

Biggest mistake I've seen time and time again is the wrong shoe in the wrong position. They ARE different front to rear.

[dmjlambert]

Thanks everybody. The consensus is the first step is make sure brakes are adjusted OK, so I will inspect the brakes carefully and adjust them.

Originally Posted by Rich69shortfleet

With drum brakes I just adjust them so I can just slip on the drums and just do some firm stops while backing up and let them adjust themselves. You don't have to back up at 80 miles an hour and stomp the pedal, just a few moderately firm stops from 5-10 miles an hour will do it. This will also tell you pretty quick if you installed the adjusters correctly. If they don't adjust, you did something wrong. But then, that's why I only ever do one wheel at a time and either reuse my adjuster or compare the new one to the one I'm taking off to make sure I'm using the correct one. Also, by doing only one wheel at a time, you can still use the other side as a reference if you temporarily forget which spring goes where or how things are supposed to fit together. Taking a picture before you start is also helpful sometimes, assuming the previous brake job wasn't done wrong!

Biggest mistake I've seen time and time again is the wrong shoe in the wrong position. They ARE different front to rear.

Please tell me after making the initial rough adjustment and putting the drum back on, how do I tell that the automatic adjuster is working and is actually making final adjustment itself after a few stops in reverse gear? I've only known the "just have faith that it probably works" method. If there is a proper way to see the automatic adjuster has actually turned and is working as intended, I would like to learn about that.

[Boog]

How about putting a dab of white paint on the adjuster wheel in one spot so you can see it through the adjuster hole? Check later to see if it moved.

[Rich69shortfleet]

Originally Posted by dmjlambert

Thanks everybody. The consensus is the first step is make sure brakes are adjusted OK, so I will inspect the brakes carefully and adjust them.



Please tell me after making the initial rough adjustment and putting the drum back on, how do I tell that the automatic adjuster is working and is actually making final adjustment itself after a few stops in reverse gear? I've only known the "just have faith that it probably works" method. If there is a proper way to see the automatic adjuster has actually turned and is working as intended, I would like to learn about that.

Well, the big indicator is that the pedal gets more firm and the brakes work higher in the pedal travel. If the adjuster(s) don't turn, the brakes don't self adjust....

[dmjlambert]

Thanks everybody. I adjusted the brakes and it is much better now. Huge difference.

I pushed down on the adjuster wheel just like the adjuster bar is supposed to do, until I felt resistance of the brake preventing the wheel from turning. Then I used a small screwdriver to hold the bar up a little bit while I turned the adjuster the other way to loosen it. On one truck wheel the bar did not contact the adjuster wheel so I did not have to hold the bar up to loosen that one. On two of the truck wheels, the bar made just a little bit of contact to the adjuster wheel. On the final truck wheel, the bar made good contact with the adjuster wheel, and as I was turning the adjuster wheel it made nice loud clicks. That one only took a few clicks to tighten up, so I think that is the only one that really self-adjusts.

So tell me, when I replace the drums and shoes, which I still have on my list of things to do, what should I do to make sure the bar contacts the adjuster wheel and works well? Is it a matter of bending the bar so it engages the adjuster wheel better? Here is an older picture of one of the brake adjusters.

[Jason Banks]

That adjuster wheel looks worn. I would replace it and as much of the other hardware as you can.

[Steeveedee]

Originally Posted by Jason Banks

That adjuster wheel looks worn. I would replace it and as much of the other hardware as you can.

Yup! Replace the adjusters (as a complete kit). Both sides, since they are likely both worn just as much as the other.

[LockDoc]

Originally Posted by dmjlambert

Thanks everybody. I adjusted the brakes and it is much better now. Huge difference.

I pushed down on the adjuster wheel just like the adjuster bar is supposed to do, until I felt resistance of the brake preventing the wheel from turning. Then I used a small screwdriver to hold the bar up a little bit while I turned the adjuster the other way to loosen it. On one truck wheel the bar did not contact the adjuster wheel so I did not have to hold the bar up to loosen that one. On two of the truck wheels, the bar made just a little bit of contact to the adjuster wheel. On the final truck wheel, the bar made good contact with the adjuster wheel, and as I was turning the adjuster wheel it made nice loud clicks. That one only took a few clicks to tighten up, so I think that is the only one that really self-adjusts.

So tell me, when I replace the drums and shoes, which I still have on my list of things to do, what should I do to make sure the bar contacts the adjuster wheel and works well? Is it a matter of bending the bar so it engages the adjuster wheel better? Here is an older picture of one of the brake adjusters.

One word. "Lubrication". You have to clean & lube all of the pivot points before they will work correctly. Including the threads on the adjuster wheel assembly.

LockDoc

[Rich69shortfleet]

Hardware kits (springs, levers, adjusters, cups, clips, etc.) are typically about $10 a wheel so get all new hardware when you do the brake job.

[Stocker]

Originally Posted by LockDoc

One word. "Lubrication". You have to clean & lube all of the pivot points before they will work correctly. Including the threads on the adjuster wheel assembly.

LockDoc

Not sure if it's the best stuff for the job, but I used antiseize on the adjusters. So far, so good.

[RichardJ]

You might want to do more than just lubricate. Lubrication can be a two edge sword. Too much lubrication attracts the dirt and in extreme can contaminate the shoe lining.

You need to clean up the loose rust and crud, inspect for excessive wear and lightly lubricate wear points as reassembling. Wire brushing the parts an a wire wheel is all that is necessary. I've never replaced springs unless they are broken.

Start be inspecting the backing plate pads. This is far more important than buying a bunch of new springs and parts that never wear out. If the shoes can't slide in/out on the pads, nothing else will make the brakes work as they should.

I've welded the pads to add material so that they can be ground/sanded flat.
Lubricate these pads, but sparingly. They're right next to the shoe lining.

[dmjlambert]

I appreciate all this great advice guys. I didn't realize the adjusters with lever and spring etc. was available in kits. Now I know what to do in order to do a better job next time.