Air pack blows air when applying brakes

[cattlerepairman]

I searched and sort-of found a few clues, but I am asking your help anyway.

1) airpack is the non-rebuildable style
2) when applying brakes lightly/normally, I could hear air escaping. Stand on the brakes at an intersection and the buzzer comes on.
3) all of a sudden yesterday, the brake pedal felt rather hard and the brake action was marginal.

System is filled with DOT5, all new wheel cylinders and flex hoses, brake reservoir mod, I did use air tool oil into the J pipe opening last fall and this spring (a little squirt).

Any troubleshooting or should I go and replace? New master at the same time?

 

[WillWagner]

Sounds like it's time to replace it. While not connected to the M/C, you are down there and you've done all the other brake components, so...

I think the rebuildable one will fit in it's place.

 

[gimpyrobb]

There is no airpack that is not rebuildable. Contact Greg(monkeyboyarmy) to see if he has any kits left.

 

[rlwm211]

I have seen where the bolts that hold the air valve cover on the side of the airpack have loosened up. I would take a look and see if that is the case. If they loosen up, that is where the air is held in check until you release the brakes. The hard pedal results form when the only pressure being applied to the brakes is your foot.

The old style airpack will fit in exactly where the new style one is now. You may have to do some minor fitting changes but nothing that is difficult.

If you can get a new styl;e airpack rebuild kit, I would do so. I would add that I would disassemble the airpack and make sure it is in fact rebuildable. Sometimes the slave bore can be so corroded that it is inadvisable to rebuild it because the amount of honing to correct the corrosion in the bore enlarges it too much.

I doubt that this is the case as your system has been working up til now. Normally such corrosion happenes when a system is empty for a long time.

Hope this helps.

RL

 

[cattlerepairman]

Thank you all for the tips. I will check for loose cover bolts and report back.

 

[Heavysteven]

That's a new one. It's like the exhaust valve is always open. I'm clueless.

 

[rlwm211]

I have rebuilt many airpacks and I have found on most that the bolts in the side that hold the airvalve piston cover in place are often loose; Sometimes less than finger tight. Since I know that some have not been tampered with that indicates to me that these bolts can loosen up. Perhaps it is a temperature pressure thing. I have not a clue.

In any event, if these bolts are loose this can cause the condition that the OP mentioned...It does not hurt to check.

RL

 

[cattlerepairman]

I have rebuilt many airpacks and I have found on most that the bolts in the side that hold the airvalve piston cover in place are often loose; Sometimes less than finger tight. Since I know that some have not been tampered with that indicates to me that these bolts can loosen up. Perhaps it is a temperature pressure thing. I have not a clue.

In any event, if these bolts are loose this can cause the condition that the OP mentioned...It does not hurt to check.

RL

2 of the airvalve piston cover bolts were indeed somewhat loose. I tightened them, but this is not where it leaks air. It leaks "high up" when the pedal is depressed. I removed the J-pipe and sprayed more lubricant in, then pumped the brakes as hard as I could without and then with air. It improved a little.

When the air pressure is up, the pedal feels as if I was pressing "against" the air assist; fighting to overcome the air resistance. Then, suddenly, pressure decreases and I can push the pedal all the way down and get "some" braking action, maybe 50-60% of what it should be.

 

[rlwm211]

From what you are saying, it sounds like the airpack has an internal leak. I can guess that it is in the compensator bore. That is where the pressure applied actuates the air assist. If the inner seal fails it allows the brake fluid pressure thatthe air piston creates feed back into the compensator bore. This is just a guess.

I would suggest that you remove the airpack and carefully disassemble the air valve and then push the compensator piston assembly out and I would bet you will find some gunk and possibly corrosion.

If you are adding oil to your airpack, I would suggest adding it to the inlet line to the air pack. This gets the lube to the air valve inlet as opposed to the exhaust portion only. I usually ssquirt some air tool oil up the copper line and then put it back together and use the brakes a few times with the air built up.

I hope this is helpful.

RL