Airpak not releasing

[wcolt45]

Fired it up,let air pressure build up,shut it down ,pulled plug in can and no pressure there,the brakes were locked last nt and this morning they're free.but as always a short drive will lock them again

 

[whyme]

in my experience when the brakes lock like this you can easily test if the air pack is holding pressure by opening the glad hand valve at the rear of the truck (driver side). if this immediately frees the brakes than your air-pack is at fault.

start the truck, build air and pump the brakes, if they lock do the above and let us know what happens.

dan

 

[wcolt45]

ok,started up,built pressure,pumped brakes enough times to lock up,jumped out with truck running and cracked the driver side glad hand and NO AIR!!! comes out ?? air will come out pass side glad hand though

 

[Capt.Marion]

ok,started up,built pressure,pumped brakes enough times to lock up,jumped out with truck running and cracked the driver side glad hand and NO AIR!!! comes out ?? air will come out pass side glad hand though

The driver side glad-hand is for service brakes, so air will only come out when you push the brake pedal... if your brakes were locked but no air was coming out, this tells you that it probably isn't your air pack.

The red, passenger-side glad-hand is the emergency one, and always has air pressure.

I'd check your rubber brake hoses. All of my brakes locked up when testing them prior to a trip, and I hopped out and had a rear hose about a hair from exploding and leaving me with no brakes.

I replaced all the hoses, and have great brakes again.

 

[wcolt45]

All new rubber lines,i tried that over the weekend,thought one may be twisted,but all look good.

 

[whyme]

ok forgive me if you answered this already, is your petal stiff? or is it still free to pump? that is while the brakes are locked.

 

[whyme]

i might suggest you remove the screw at the back of the air-pack (older style long canister) or the tube that connects to the back to double check if that releases any air, if so do the brakes free? i say this because the glad hand line could (doubt it but..) be blocked somehow. its always worth a check.

additionally it could be mechanical binding or failure within the pack itself or maybe a problem with the MC. its hard to narrow when everything is new. i don't expect that the problem is after the air-pack if all the wheels are effected, if only one or two are binding (and all are properly adjusted) then that's another story.

 

[wcolt45]

checked plug and no air,pedal after repeated pumping gets very stiff,running out of things to consider,although i noticed when driving and it does this it seems to affect the rear wheels first,there again ,new hoses ,blew out lines, shoes adj properly ,i dunno

 

[whyme]

effecting them fist is expected but ultimately if they all bind then the problem is upstream. once they lock if you open the brake bleeder on the air-pack do they release?

 

[wcolt45]

No ,bleeder does nothing,if i crack the fluid line at airpak it will release,makes me think its not a line at axles

 

[whyme]

when you say fluid line do you mean the brake line leading from the air-pack to the wheels?

 

[wcolt45]

yes,can crack that fitting in the airpak and frees them up

 

[whyme]

then your air pack is binding. remove and replace or rebuild. id check those two issues as mentioned in the TM first. also look for debris in the air-pack. mine was full of crud. i know you replaced most of the system but if there was anything left in there it could have gotten somewhere it shouldn't have.

good luck, sorry this wasn't a quick fix.

 

[dragonwagon]

The driver side glad-hand is for service brakes, so air will only come out when you push the brake pedal... if your brakes were locked but no air was coming out, this tells you that it probably isn't your air pack.

The red, passenger-side glad-hand is the emergency one, and always has air pressure.

I'd check your rubber brake hoses. All of my brakes locked up when testing them prior to a trip, and I hopped out and had a rear hose about a hair from exploding and leaving me with no brakes.

I replaced all the hoses, and have great brakes again.

Been reading and thinking on this , I agree on the rubber hoses . They can colapse inside and wont let fliud back . Seen it on old motor homes and stuff several times . Acts like a caliper hung and its a hose .

 

[whyme]

Altho plausible that wouldn't explain why releasing pressure at the air-pack would free them entirely. Also it's unlikely that all three main rubber lines would simultaneously fail.

 

[scrapdaddy]

Sorry you're having pains with your brakes, but I would like to thank everyone for responding. I have learned alot about finding brake problems. Please keep us posted on your fix. Good luck! Ron

 

[wcolt45]

I also would like to tkank everybody as well,i disassembled most of my airpak while still on the truck just to see if everything was in place and didnt find anything abnormal,lubed it a bit while apart and put it back together,now its raining and have to wait to see if anything changed

 

[Monkeyboyarmy]

Just for your info,I recently had the exact same issue. I rebuilt the master cylinder with no luck. Switched out the airpack with a known good one and the problem went away.Good luck with yours.

 

[bugei]

when you rebuilt the airpack according to the tm, did you see the warning in the stickies about the error in the tm? the tm has the small cup being reversed from correct. which makes for an exciting few minutes of lots of pedal and no brakes. i suspect that this error in the tm may be your issue.

new info!

oh oh, i see that the sticky about the error in the tm did not make it over from the old site. would someone PLEASE put it back up there from the old site!!

 

[wcolt45]

you are referring to the piston cup and the pushrod seal?