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  1. #1
    Independent Owner/Operator Hanadarko's Avatar
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    Bendix AD-IP Air Dryer question..

    I replaced my AD-IP air dryer and Tru-Flo 550 about a year ago.
    I replaced the Bendix Air Governor last spring and used a 105 cut in by 120 cut out.
    So most of the equipment is recent. I did not use reman parts, all were new.

    Things seemed to be ok but recently I noticed a possible problem but not sure if it's normal:
    My air system reaches 120psi in primary and secondary and then the AD-IP blasts.
    Orange needle stays around 120 and the green needle falls after the purge. Orange needle does not move.
    I figure this is normal.



    Air PSI continues to drops a bit (as expected) and then soon after that, air PSI seems to rebuild back up to 120
    and then the AD-IP blasts again.

    If I run the system right up to about 120psi, just before the purge and then shut the engine off, the PSI
    in both systems will remain at 120 for well over an hr...sometimes even longer than that if its not windy out.
    I dont believe I have a leak anywhere and do not hear anything when crawling around and under.
    A few months ago I soaped up things and didnt see any leaks either.

    I guess what I am trying to ask is that I hear this purge then refill then purge in a consistent basis.
    Not sure if that is normal operation or if I have something I should check.
    I would think that once it charged and purged, unless something is calling for air or there is a leak, why does
    this cycle continue like it does?

    Anyone have any thoughts?

  2. #2
    Road Train Member Heavyd's Avatar
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    Sounds like the delivery check valve in the discharge port of the drier is not working and allowing system air in your primary tank to leak back out of the dryer during a purge cycle.

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  4. #3
    Medium Load Member Gear head's Avatar
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    If I remember correctly there is a plug where a small plastic stopper with an o-ring and a spring. I found the o-ring was cut. I changed the governer the unloader in compressor no change but that little o-ring was the culprit. It is located in the air dryer in one of the ports Im pretty sure its behind a plug. If not its your unloaders in the compressor. Is your governer at the air dryer or on compressor? If it's on the dryer you can check the unloaders by unhooking the line that goes to compressor from the governer and blow air in it if the compressor stops building air then the unloaders air good. You can tell when compressor stops building when airdryer stops making that clicking sound. But im willing to bet its that little o-ring I spoke of. Sorry that I can't tell you exactly where it is it's hard because im not looking at the dryer. This o-ring and spring is in airdryer sorry for the confusion.

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  6. #4
    Independent Owner/Operator Hanadarko's Avatar
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    My governor is mounted to the Tru-Flo compressor...

    How often was your's popping off?

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    Medium Load Member Gear head's Avatar
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    about every 15 to 30 sec.

  8. #6
    Independent Owner/Operator Hanadarko's Avatar
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    Ok. I dont think mine is that bad.....I never thought to time it but its consistent.
    could be 60 secs....I guess.

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    Since your governor Is mounted to the compressor make sure it's tight, they tend to rattle loose and the problem your describing sounds like that, also since it's a high heat area sometime the gasket between the governor abd comp becomes crusty and cracks

  10. #8
    Independent Owner/Operator Hanadarko's Avatar
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    Quote Originally Posted by Ashman_42 View Post
    Since your governor Is mounted to the compressor make sure it's tight, they tend to rattle loose and the problem your describing sounds like that, also since it's a high heat area sometime the gasket between the governor abd comp becomes crusty and cracks
    Ok...I did some more troubleshooting and this is what I found:

    1. Soaped up the governor and all of the fittings. No leaks/bubbles.
    2. Soaped up all fittings on the AD-IP. No leaks/bubbles.
    3. The dryer purges about ever 35 seconds at fast idle (950 rpm)
    4. After the dryer purges, I can feel some air continue to blow out the purge port for about 15 seconds.
    (its consistent but not full pressure) - dont know if thats normal or not.

    Per Bendix:

    "However the purge valve will remain open and will not close until air brake system pressure is reduced and the governor signals the compressor to charge the system. "



    I also discovered that if I fan the brakes to kick the governor in and then run the engine at 1300 RPM
    the system will fill - dryer will purge and then it won't after that.

    If I then return the 1300 RPM back to reg idle (after 10 seconds after the purge),
    I can let it idle for 10mins or more and no loss of air nor any further purge.

    I can hear the governor activate (slight psst sound when air drops to 105PSI) so I believe its running fine.

    Does this point to anything better?

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    Quote Originally Posted by Hanadarko View Post
    Ok...I did some more troubleshooting and this is what I found:

    1. Soaped up the governor and all of the fittings. No leaks/bubbles.
    2. Soaped up all fittings on the AD-IP. No leaks/bubbles.
    3. The dryer purges about ever 35 seconds at fast idle (950 rpm)
    4. After the dryer purges, I can feel some air continue to blow out the purge port for about 15 seconds.
    (its consistent but not full pressure) - dont know if thats normal or not.

    Per Bendix:

    "However the purge valve will remain open and will not close until air brake system pressure is reduced and the governor signals the compressor to charge the system. "



    I also discovered that if I fan the brakes to kick the governor in and then run the engine at 1300 RPM
    the system will fill - dryer will purge and then it won't after that.

    If I then return the 1300 RPM back to reg idle (after 10 seconds after the purge),
    I can let it idle for 10mins or more and no loss of air nor any further purge.

    I can hear the governor activate (slight psst sound when air drops to 105PSI) so I believe its running fine.

    Does this point to anything better?

    well here is where me my father and the guy we are leased to are at. after a year we have all replaced multiple air componets. all of us are on a seventh dryer as this is where the problem ends up at. now according to the shops the dryers went bad because of the governor. but after we told them those had been replaced several times they said it was the compressor causing the dryer to burn up but again told them we had replaced them a few times during all this. we have contacted bendix and submitted copies of purchases and install dates mileage showing use. they are looking into the problem and say there could be a issue with the dryers and a possible redesign...till than i bypassed the dryer and have not had any other issues. just have to drain tanks every day or two

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  13. #10
    Independent Owner/Operator Hanadarko's Avatar
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    Quote Originally Posted by carrkool View Post
    well here is where me my father and the guy we are leased to are at. after a year we have all replaced multiple air componets. all of us are on a seventh dryer as this is where the problem ends up at. now according to the shops the dryers went bad because of the governor. but after we told them those had been replaced several times they said it was the compressor causing the dryer to burn up but again told them we had replaced them a few times during all this. we have contacted bendix and submitted copies of purchases and install dates mileage showing use. they are looking into the problem and say there could be a issue with the dryers and a possible redesign...till than i bypassed the dryer and have not had any other issues. just have to drain tanks every day or two
    Well I guess I dont feel bad. I dont understand why higher RPM (1200+) keep things happy though.
    I suspect that could be a clue since I cant find any leaks anywhere and she holds air all night (although it does taper off over time)

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