What all runs on vacuum?

[Selahdoor]

I was not under the impression that pumping the brake pedal would adjust the brakes.

Only that if it was taking a while for the rear cylinders to fill, as @snicklas suggested... pumping them might help to fill them more quickly.

Agreed about the master cylinder. I am beginning to suspect that is the case.

 

[1mouse3]

The rear brakes should auto adjust brake checking in revese, that is if the adjusters have not fallen off. Mine keep falliing off and have had to put one of them back on the 4 times I have pulled the back wheels, also moving any with the ebrake on removes any progress you have made. So can get it to the point the ebrake works good then it gets messed up again, think one the adjuster have fallen again so they somewhat work.

 

[TNBrett]

The main thing that caught my attention was that a vacuum leak equals a stiffer pedal. What you describe sounds more like air in the system somewhere still. If the pedal sinks with steady foot pressure, then the master cylinder is leaking past the piston. If there’s air in the system it’s like having a spring between your foot and the pedal. For light to moderate braking it may not be that noticeable, but when you push harder that spring has to be compressed.
When the brakes were bled did you bleed the ABS valve. It’s part of the bleeding process on these trucks. The proper order is RR, LR, ABS valve, RF, LF. If you had the rear lines open, the ABS has to be bled. It has a normal bleeder screw on it, just bleed it the way you would any other caliper or wheel cylinder.

 

[subway]

The main thing that caught my attention was that a vacuum leak equals a stiffer pedal. What you describe sounds more like air in the system somewhere still. If the pedal sinks with steady foot pressure, then the master cylinder is leaking past the piston. If there’s air in the system it’s like having a spring between your foot and the pedal. For light to moderate braking it may not be that noticeable, but when you push harder that spring has to be compressed.
When the brakes were bled did you bleed the ABS valve. It’s part of the bleeding process on these trucks. The proper order is RR, LR, ABS valve, RF, LF. If you had the rear lines open, the ABS has to be bled. It has a normal bleeder screw on it, just bleed it the way you would any other caliper or wheel cylinder.

for what it is worth I agree with Brett from how the problem was described.

It would still be worth pulling the rear brake drums and taking a look at the rear brakes. You dont mention loosing any brake fluid. I could believe that the rear caliper was damaged from heat when dragging and leaking when you pressed ******* the master cylinder. A visual inspection would tell you very quickly if that were the case. If you are not loosing fluid though it is getting bypassed internally in the master.

 

[Big Bart]

Can you be more concise?

1) You loose power braking? Pedal moves a little towards you and it gets harder to push the brake pedal to stop?

2) Or your brake pedal slowly moves all the way to the firewall then stops at its max movement forward.

3) Your brake pedal seems to stop but moves another inch or so slowly and stops.

4) Other?

If #1 that is likely your booster or vacuum to it.
If #2 that is likely your master cylinder if your not losing brake fluid, or if your loosing fluid a brake leak.
If #3 there could be an outside chance you have a ballooned rubber brake line or a clogged line and brake fluid slowly goes through it. So it gets firm then the pedal sinks a little.

 

[Big Bart]

Ok re-read the thread. If at a stop by pushing harder your brake pedal sinks more and more and then all the way to the floor. That sounds like a bad master cylinder as you state no loss of fluid.

If it went say a inch more but not to the floor, that sounds like air or a plugged hard line or ballooned or ballooning brake hose.

Ditto on adjust the rear brakes next. But better to inspect then adjust.

 

[kbenz]

That was my first thought, too. But it's a new booster. Less than 3k miles on it. Ergo, maybe just a vacuum leak. Got to check out the easy stuff first. Booster might even have a warranty on it if it comes down to that.

I got a bad master cylinder out of the box before

 

[Cubey]

I was not under the impression that pumping the brake pedal would adjust the brakes.

This is how the mechanism works. No need to pump it. Normal braking should adjust it. I was using the parking brake lever but normal braking should also make it work. Of course with the drum on, it limits how far it can go out unlike with the drum off in this video, where it would just keep going. If it's functioning properly (as in this video, all new parts) then it should self adjust under normal driving conditions.

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[chillman88]

This is how the mechanism works. No need to pump it. Normal braking should adjust it. I was using the parking brake lever but normal braking should also make it work. Of course with the drum on, it limits how far it can go out unlike with the drum off in this video, where it would just keep going. If it's functioning properly (as in this video, all new parts) then it should self adjust under normal driving conditions.

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I would like to mention, that when I replaced my brakes the brand new adjusters did absolutely nothing. I'm sure some of it is a quality issue with inferior parts but it's well know that the automatic adjusters on these are pathetic so I would never rely on them.

I'm not trying to contradict anyone who has a set that works, just pointing out that it's not a good idea to EXPECT them to work properly.

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Brand new "wearever" brand, all properly greased. Motorcraft might work better but I don't know.

 

[Cubey]

I would like to mention, that when I replaced my brakes the brand new adjusters did absolutely nothing. I'm sure some of it is a quality issue with inferior parts but it's well know that the automatic adjusters on these are pathetic so I would never rely on them.

I'm not trying to contradict anyone who has a set that works, just pointing out that it's not a good idea to EXPECT them to work properly.

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Brand new "wearever" brand, all properly greased. Motorcraft might work better but I don't know.

You have to position the arm just so or it will skip the teeth. Yours might be positioned a bit too high so it can't grab on. Also, the teeth in the screw do seem to wear out and should be replaced. The self adjusting kits are $10 for each side From O'Reilly and you get this in each kit:

You must be registered for see images attach

 

[chillman88]

You have to position the arm just so or it will skip the teeth. Yours might be positioned a bit too high so it can't grab on. Also, the teeth in the screw do seem to wear out and should be replaced. The self adjusting kits are $10 for each side From O'Reilly and you get this in each kit:

You must be registered for see images attach

Yeah I had replaced EVERYTHING. I couldn't see any way to adjust the location of the arm, since the location is directly related to the pivot pin and the spring tension.

 

[Cubey]

Yeah I had replaced EVERYTHING. I couldn't see any way to adjust the location of the arm, since the location is directly related to the pivot pin and the spring tension.

As I recall, I had to kind of pull it downward and push it into the teeth to make it catch. Then it worked properly like in the video. The springs aren't strong enough to force it into place. of course once you start messing with it from the outside with the drum on, it's anyone's guess if it stays put, but it should if you hear it clicking when you are turning the star wheel. But if the clicking happens, it should be working... I would think.

 

[franklin2]

I will also say I have never had the auto adjusters work on my truck. They also don't work on my Chevy Tahoe. It's a sure recipe for warped front rotors unless you go back and manually adjust them every 6 months.

 

[TNBrett]

The auto adjusters worked too good on my truck. Until I got the parking brakes returning like they should, mine would keep tightening up until they were seriously dragging.

 

[kbenz]

I've never had auto adjusters work on anything