Mack _ Cummins air compressor won’t build air pressure

In this video I diagnose why a mack wabco air compressor isn’t building air pressure.
I attribute my successes to god and give him the glory.
The eyes of the lord are in every place, beholding the evil and the good. (Proverbs 15:3)

[@TJJohnson-ik6yd]

You done a great job on this video and answered all my questions. Thanks

[@larrycroft470]

This was interesting!!! Great video.

[@kc360awareness]

Nice job working through the problem. I kept thinking how can it build air, but not build air? Those governor valves are super simple and the unloader seemed to be the most likely culprit….. then you bust out the drier as a possibility. Doh! How simple, and really a matter of maintenance anyway. Those driers have a service interval of some sort. I know my pea brain tends to go straight to the most complicated stuff first. Gotta keep it simple.

[@JasonTheMunicipalMechanic]

I wouldn’t be too hard on yourself, I thought it was the compressor more than I though it was the air dryer. It made more sense to me after I took the air dryer apart and saw how it functioned and the corroded inlet check valve. I could have saved some time and work if I checked the air dryer first.

[@kc360awareness]

@@JasonTheMunicipalMechanic yeah about halfway through I remembered watching your shorter video with the drier autopsy. Then it all made sense. Our buses have AD9 driers they are made a little different. They have a check valve on the inlet to keep the pressure from bleeding back through the compressor. I’ve also heard of older Cummins where the compressor “needs” a little pressure on it work right. Guess if a guy knows about the system design it helps. Being a Jack of all trades in the fleet world makes it a little more difficult to do that part well.

[@edwardrivera2844]

Thanks for the video

[@musahawkins8765]

Alot of times too your hot line the steel braided from the compressor will start to seep out you can't see it unless you spray with soapy water it will act like a weak compressor good thing to check

[@JasonTheMunicipalMechanic]

Thank you for the tip. I’ll keep that in mind.

[@patrickhathaway6178]

Interesting video. Thanks.

[@JasonTheMunicipalMechanic]

Thank you Patrick.

[@craigdreisbach5956]

Jason. Great troubleshooting and teaching. I will never be working on this type of rig, but I'm wondering if the electrical connection to the dryer is some sort of heating element to prevent the condensate from freezing. Kind Regards, Craig

[@JasonTheMunicipalMechanic]

Thank you Craig. You are correct, the plug on the dryer is a heater to keep it from freezing. I’ll have a short video coming up on what the problem with the air dryer was.

[@annierenard5954]

good video, thank you

[@JasonTheMunicipalMechanic]

No problem Annie. I appreciate you watching.

[@Tom-pn5sk]

So when it downloads IT Supplies air to the compressor to shut off the air to the dryer? 🤔

[@johnwinden8511]

Interesting video. Do you change your air dryer filters? We changed ours annually per instructions from International.

[@JasonTheMunicipalMechanic]

I’ve actually never changed an air dryer filter. We don’t get many miles on these trucks and this is the first air dryer I’ve had to change in the 10 years I’ve been a town employee. I actually cut open the filter just to see what was inside and to see if it was clogged and it looked brand new inside still.

[@wildman9364]

I have seen tons of air dryers fail intermittently but never a compressor fail intermittently always see them fail and stay broken. not saying it cant happen cause it still can. Cheers

[@JasonTheMunicipalMechanic]

Thank you wild man, I appreciate your insight.

[@wildman9364]

@@JasonTheMunicipalMechanic Cheers

[@Tom-pn5sk]

Bottoms up 😊

[@ericcorse]

Are the two air pressure gauges one on each tank? I like the 140 mph speedo but it might be a little optimistic.

[@JasonTheMunicipalMechanic]

Yes one is for the primary and one for the secondary. Yes 140 is a touch out of reach😁. I think this truck tops out at 65. It would probably go 140 if it was dropped out of the sky. I used to drive a Peterbilt about 10 years ago that would go 100, but that speedo I think said 90 on it. The needle just keeps going around.

[@ericcorse]

@@JasonTheMunicipalMechanic It makes me wonder if they got a deal on those speedos

[@foxbodyguyeightyeight3672]

They use the same speedo for Canadian market but it's calibrated for kmph it's cheaper for them to leave it the same for both markets

[@JasonTheMunicipalMechanic]

That makes perfect sense

[@ericcorse]

@@foxbodyguyeightyeight3672 Thanks

[@sundownerwhoopwhoop5016]

Why the hell you don’t change just the filter 😂and you’re the mac

[@davidwellnitz5811]

Hello my name is Dave and at my work we got a 1978 GMC brigadier grain truck and one day I was using it and it works fine and next day my boss starts it up and it won't build air pressure and I don't know what's wrong with it I know I found the air compressor and it's on the back side of the Detroit engine in the doghouse inside the cab so I don't know if it's air compressor I know I took the line off and and it's he was pushing air but very little it was going like it was just like hissing a little but it's not building up air pressure. And I've talked to a few people that work on trucks and they don't have no clue what's wrong with it because it's so old maybe you would know what I could do to fix it if it's one lubrication in there I know when I took the line off and it was hissing a little there was like oil all over my hands so I don't know if it's not getting no lube or what but I'm not a diesel mechanic so I don't know thank you and God bless

[@JasonTheMunicipalMechanic]

There is an unloader valve in the compressor head that diverts the air when it is charged so it doesn’t over charge the air tanks. The compressor runs constantly so that is how is stops charging. First you are going to need to verify that it is the compressor, if it is and your not getting much air out I would check the unloader valves. Different compressors do it differently and some are easier then others. You could have a problem with the governor also which is the part that controls the unloader valves on the compressor. Try this video kzbin.info/www/bejne/qGaqmHh7iJ2KpNU

[@davidwellnitz5811]

So on top of the air compressor there is this bolts that must go into the head can a person take them both off and lift the cover off and see what's inside? In front of the compressor there is like a round canister with a screwed on cover and it looks like it's got a bolt in there in the spring and I took them horses off and I got air pushing a little bit of purging air pushing from a black hose into there but nothing coming out of the one side but then I take the big holes off of the air compressor and there's a little bit of air coming out of there but it's like purging out and and then when I held my finger there it was like a little bit of oily stops and coming out with it.

[@davidwellnitz5811]

Could I put some kind of cleaner in there like some carburetor cleaner or brake cleaner in spray it in there to the outlet that that sucks air from like the air cleaner and see if that would help then maybe clean and maybe get that valve on stock?? I don't want to put anything in there if it if it's going to harm the air compressor thank you and God bless

[@JasonTheMunicipalMechanic]

I wouldn’t put any cleaners through the compressor. A compressor is basically a small engine and needs oil to lubricate it. A cleaner will wash the oils off and cause damage. Did you watch the video I included to clean up the unloader valves? Do you know what type of compressor it is you have?