1. Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
  2. ALL NEW MEMBERS READ THIS FIRST!! Thank you for joining Heavy Equipment Forums! If you are new to forums we communicate with "Threads", please search our threads to see if your topic may have already been answered and if not then click "Post New Thread" in the appropriate forum. This will allow all of our members to see your question and give you the best chance to be answered. After you've made a number of posts you will graduate to Full Member status where you'll see a few more privileges. Following these guidelines will help make this the best resource for heavy equipment on the net. Thanks for joining us and I hope you enjoy your stay!!

ISX air issue

Discussion in 'Trucks' started by Shimmy1, Jan 16, 2022.

  1. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    Anyone ever had issues with an ISX eating air governors? Have put two on in a few months. Air dryer is new. What happens is you will start hearing air bypassing the purge valve on the dryer when you're in a good pull (high boost), and it won't build air until you let up on the pedal. Then, it'll be like you have a slow leak in the system, compressor will kick on about every 5 minutes or so. Eventually, it will be down to a minute per cycle. Change the governor, it will be fine for a couple months. Anyone see this before?
     
  2. stinky64

    stinky64 Senior Member

    Joined:
    Feb 25, 2017
    Messages:
    425
    Occupation:
    big truck wrench/fixer of things
    Location:
    java center ny
    Sounds like a bad unloader valve in the compressor head, over time they carbon up and stick open or closed..You can try putting house air directly to the unloader with the truck running and if it keeps making air there's your gremlin.. you can usually just swap out the head if your compressor is still good mechanically..Another sign of a bad head is pressure in the cooling system, any issues there?
     
    DB2, JPV, Shimmy1 and 1 other person like this.
  3. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    No issues there. Why does it work fine for a while, then slowly degrade? And where is the air bypassing to get to the dryer? It doesn't overpressure, when the dryer purges it stops pumping. The telltale is the farting purge valve under boost, and then the gradually increasing leakdown of the wet tank causing the compressor to kick in. Eventually, it will kick in after only losing about 5 lbs on the gauge. Right now, it will bleed down to compressor cut-in.
     
  4. JPV

    JPV Senior Member

    Joined:
    Aug 20, 2015
    Messages:
    709
    Location:
    S.W. Washington
    That is exactly pretty much the symptoms of an unloader valve, if you have already changed the governor it's about all it can be I believe. I can't explain why changing the governor helps for a while though. I have never replaced one on an isx but quite a few of whatever compressors Cat uses, they generally are completely carboned up.
     
  5. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    Can you clean them up, or can they be rebuilt? Is a new compressor in my future?
     
  6. JPV

    JPV Senior Member

    Joined:
    Aug 20, 2015
    Messages:
    709
    Location:
    S.W. Washington
    I have always been able to get a kit for the unloader on anything I have needed, I would assume your compressor would be no different. It usually consists of the spool and spring or whatever hard parts that are in there and o rings or gaskets. I can't say for sure what yours is like though.
     
  7. Birken Vogt

    Birken Vogt Charter Member

    Joined:
    Nov 30, 2003
    Messages:
    4,279
    Location:
    Grass Valley, Ca
    Sometimes you can also get a rebuilt head for the compressor.
     
    JPV likes this.
  8. Truck Shop

    Truck Shop Senior Member

    Joined:
    Dec 7, 2015
    Messages:
    10,300
    Occupation:
    star gazer
    Location:
    SE Washington St
    PAI.
     
    Shimmy1 likes this.
  9. Tenwheeler

    Tenwheeler Senior Member

    Joined:
    Dec 15, 2016
    Messages:
    828
    Location:
    Georgia
    If it is a Wabco compressor I have just replaced the head on a bunch of them. Got them from Bepco.
     
    Shimmy1, JPV and Truck Shop like this.
  10. Truck Shop

    Truck Shop Senior Member

    Joined:
    Dec 7, 2015
    Messages:
    10,300
    Occupation:
    star gazer
    Location:
    SE Washington St
    Tenwheeler likes this.
  11. stinky64

    stinky64 Senior Member

    Joined:
    Feb 25, 2017
    Messages:
    425
    Occupation:
    big truck wrench/fixer of things
    Location:
    java center ny
    No matter if you replace the compressor or just a new compressor head, make sure to inspect/ clean the discharge line from the compressor it's probably full of carbon as well...
     
    JPV likes this.
  12. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    The EGR hasn't worked for.........ever..
     
  13. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    I'm replacing the compressor. More details later, but for now.......

    How big of a deal is timing it? Have several guys say not to worry about it since new compressors don't even have marks anymore? Tried getting the plug out for the timing pin and that don't remove either......
     
  14. stinky64

    stinky64 Senior Member

    Joined:
    Feb 25, 2017
    Messages:
    425
    Occupation:
    big truck wrench/fixer of things
    Location:
    java center ny
    Wouldn't worry so much about actually "pinning" the motor but at least line up the pinning marks on the balancer and if the new compressor has marks line them up, there are a couple of short you tube videos that show the process..It's not an injection pump buuut..I've only done one on an ISX but I did line up the marks just cuz.. May be the reason the compressor head failed was the fact that egr $hit the bed, I don't know if all, but some ISX systems the compressor got supply from the egr system to recirculate all that good exhaust air:rolleyes: engineers, gotta love 'em...As previously said, make sure you check the discharge line for carbon build-up as well..otherwise you run the chance of that crap dislodging from the line and corrupting the dryer/governor etc. again as well..
     
    Shimmy1, JPV and grandpa like this.
  15. grandpa

    grandpa Senior Member

    Joined:
    Oct 15, 2009
    Messages:
    1,930
    Location:
    northern minnesota
    Agree, the guy that thought up pulling exhaust gas into the air compressor otta be kicked in the nads.
     
    stinky64 and Tags like this.
  16. pushbroom

    pushbroom Well-Known Member

    Joined:
    Feb 4, 2017
    Messages:
    85
    Location:
    Saskatchewan
    Common rail/def ISX 2250 and up dont need the compressor timed. Anything before that does. Timing is done for noise, they can sound quite bad if they are out. Spin the engine over to insert pin first then r+r compressor.
    Quickserve will let you make an account and get all the info for 5 engines. I can also post the procedure if you give the serial number.
     
  17. Birken Vogt

    Birken Vogt Charter Member

    Joined:
    Nov 30, 2003
    Messages:
    4,279
    Location:
    Grass Valley, Ca
    Compressors had discharge line carbon pluggage bulletins long before EGR was ever even thought of. Just the temperature mixed with a little oil blowby can make carbon. I never worked on an EGR/compressor setup, didn't know it was a thing, but if it were mine, I would consider just plumbing it to 0 psi filtered air instead. I never did see much point in turbocharging the air compressor, it makes air real fast when you have your foot into it, but the only time you need a lot of air is idling around a parking lot anyway.
     
  18. Shimmy1

    Shimmy1 Senior Member

    Joined:
    Aug 14, 2014
    Messages:
    3,346
    Location:
    North Dakota
    Got it swapped. Had to change radiator out today also, so without the radiator in the way, we could look in the hole in front and verify the old compressor was timed properly. The guy we've had do engine work on this truck before was nice enough to paint "pin" on the damper, so after lining that up with the cover, we could see the "X" on the compressor gear, and see it was lined up with the notch.

    After putting shop air to the truck today, we could hear air leaking internally by the compressor. After removing the output line from the compressor, we found air leaking from the compressor. Hooked that back up, unhooked the purge line from the governor, and had air leaking there while it was supposed to be pumping. Started the truck, and while the compressor was pumping, there was air pulsing out of the signal line port. No one locally had a rebuild kit, so I just put a new one on.
     
    stinky64 and JPV like this.
  19. stinky64

    stinky64 Senior Member

    Joined:
    Feb 25, 2017
    Messages:
    425
    Occupation:
    big truck wrench/fixer of things
    Location:
    java center ny
    Don't know if you need to return the core or not, but just for $hits and giggles you can still pull the compressor head off just so you can see what makes 'em tick....I always do with any new contraption, just can't help myself...