air dryer blows off too much

[felicello122]

new dryer, new tanks, new governor, and unloader valves. On a 94 ch model, something not holding pressure?

[Challenger]

Whats to much? Every few second? Is this the reason for all the parts being replace? Does it build air to 125ish and continue to purge? What exactly does it do?

Check the signal lines coming from the governor. Check routing, check for holes from rubbing.

[felicello122]

Whats to much? Every few second? Is this the reason for all the parts being replace? Does it build air to 125ish and continue to purge? What exactly does it do?

Check the signal lines coming from the governor. Check routing, check for holes from rubbing.

Blows off about every minute to minute &1/2, air dryer was changed for service, it does build air to 125, it just cycles to frequently. Signal line was replaced, no leaks in lines, orginal set up and routing.

[MidniteMechanic]

Do you mean a complete air drier or just the dessicant cartridge replaced? If just the cartridge, was the purge valve rebuilt and possibly cut an O-ring?

I would suspect a bad check valve on either the drier or the wet tank. It will bleed air out the purge valve if one of them is leaking.

[felicello122]

Do you mean a complete air drier or just the dessicant cartridge replaced? If just the cartridge, was the purge valve rebuilt and possibly cut an O-ring?

I would suspect a bad check valve on either the drier or the wet tank. It will bleed air out the purge valve if one of them is leaking.

was a complete dryer from mack, blows off and the green needle (air guage) drops all the way to 90 PSI and the cycle repeats.red needle drops to about 105 psi.

[Challenger]

Sounds like you're replaced everything. Was the problem there before all the repairs? Was this the reason for all the repairs? Does this happen while the truck is at idle? Can you hear the air leaking past the air dryer purge valve when its dropping from 125-90? If you can hear leaking past the air dryer purge valve I would consider swapping it out with a known good one. Sometimes new parts can fail off the get go. I end up running in circles because its hard to condemn a new part.

[macks4me]

Try one thing. If possible bypass the drier to see if you still have a air loss.

[felicello122]

Try one thing. If possible bypass the drier to see if you still have a air loss.

Air dryer failed, thats why i replaced it, I am going to bypass it to see if the new one is leaking inside somewhere. thanks for the replys.

[rsb502]

You have an air leak somewhere if your dropping to 90 psi, j had a 93 that popped off repeatedly it was bad unloader seals in the head on the air compressor, $40 kit from Bendix. I would guess it was something else however because if the signal line, unloaders, or dryer are leaking signal pressure and causing the dryer to pop it would not drop pressure on the guage, that denotes a leak in the primary air system. I have fixed this several times and any time it was the signal to the governor/dryer it never dropper more than 5 psi on the guage. I know you have looked but I would say check for a leak somewhere in the primary system, just out of curiosity does it happen with the brakes set and released?

[felicello122]

You have an air leak somewhere if your dropping to 90 psi, j had a 93 that popped off repeatedly it was bad unloader seals in the head on the air compressor, $40 kit from Bendix. I would guess it was something else however because if the signal line, unloaders, or dryer are leaking signal pressure and causing the dryer to pop it would not drop pressure on the guage, that denotes a leak in the primary air system. I have fixed this several times and any time it was the signal to the governor/dryer it never dropper more than 5 psi on the guage. I know you have looked but I would say check for a leak somewhere in the primary system, just out of curiosity does it happen with the brakes set and released?

doesn't matter with the brakes,or if idiling or driving always the same results.

[felicello122]

new drier isleaking inside, problem solved

[rsb502]

BAM! theres a little chef Elzar for ya! anybody know chef Elzar? Yeah just because its new doesnt mean its right its happened before they get in a hurry and you get shit for parts.

[Challenger]

I hate when new parts fail, so much time ends up getting wasted.