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I give up!!! Air Compressor system trouble


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Im at the end of my rope! 2012 Mack red engine MP7, rebuilt Wabco Compressor, new governor, working dryer but not sufficient enough air. It takes me 5 mins of 1600rpms to build up to 90psi. If I lower the rmp's, it goes down to 50 psi. no leaks. The primary tank is stopped up but I don't know with what. I bypassed the primary tank and air dryer and still can only get 90psi.  This truck sat for 2 years so I'm thinking maybe oil was in the tank and dried out? Ive never experienced this problem before. My mechanic can fix anything and he is stumped...

Any suggestions would be greatly appreciated. 

 

Edited by Miriam Romero
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yahr wot seed sed

we have a mack th@ passes a bit of oil down to the 1st tank, the oil n heat carbonizes n clogs up the main pipe th@ restricts the air flow

also if U drain all the air tanks n put the shop air in the 1st tank n see n listen to where the air is go n

cya

 

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5 hours ago, Swishy said:

yahr wot seed sed

we have a mack th@ passes a bit of oil down to the 1st tank, the oil n heat carbonizes n clogs up the main pipe th@ restricts the air flow

also if U drain all the air tanks n put the shop air in the 1st tank n see n listen to where the air is go n

cya

 

Thanks, I will try that! 
Im hoping its not the New/rebuilt compressor. Those things aren’t easily accessible.

thanks for your suggestions!

miriam

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6 hours ago, Hayseed said:

I would Check that the Airline from the Compressor to the Wet Tank isn't carboned Up..

I will do that! Thanks for commenting. I’m at my wits end with this! 30+ years in trucking, married to a Mack specialist who’s mentor is a Mack teacher and they are stumped! I guess computers can diagnose and fix everything🤷‍♀️
thank you for your suggestion! I will check that line!

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IF U suspect the new compressor is not up to scratch

U could use a stethoscope to hear wots go n on

the ozzie bush stethascope = a long handle screwdriver place end on compressor with engine running

place thumb on end of screwdriver handle place ear on thumb

WotSezU?

cya

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17 hours ago, Miriam Romero said:

The primary tank is stopped up but I don't know with what.

I just noticed This ^^^^ it needs to be sorted our First.. In My opinion..

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"Be who you are and say what you feel...
Because those that matter...
don't mind...
And those that mind....
don't matter." -

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5 hours ago, Hayseed said:

I just noticed This ^^^^ it needs to be sorted our First.. In My opinion..

  •  

We are going to try all of these suggestions tomorrow. We have a tiny Snap On camera On a wire that’s we are going to try to send into the primary tank.

thank you all for taking the time to comment and suggest on my dilemma. 
I will report back on our findings. 

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Just my two cents worth, you're assuming the new governor and the compressor you put on are good.  I would first replace the governor, maybe the compressor, and find your air leak.  We've had to replace a lot of new and reman parts lately.  Your pressure drops from 90 to 50 when your rpm's drop.  Where's the 40 lbs of pressure going?  JMO

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My husband said that he could blow through it until it heated up and it would swell up inside of the hose once heated and he couldn’t blow through it. 
The only place open 24/7 that may by chance have that braided hose is Freightliner in Houston. This tank has fine metric threads and I’d bet that Mack is the only place to get it. The new air tank had an extra hole so we had to get a plug from Mack this morning. 
Thanks again! I’m grateful for your input. I do believe we are back in business...with a whole new air brake system😂

 

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I always run type "K" copper pipe for the discharge of the air compressor to the drier, or wet tank. This is a heavy wall type copper pipe and work hardens when you bend it but excels at both cooling the discharge air from the compressor, and condensing out the moisture due to the cooling effect. Don't attempt to bend type "K" pipe by hand as it will readily kink in the bending area.

I've seen the newer "teflon" stainless braided discharge hose used a lot and it works well but is expensive; albeit much easier to run. Anything needs support and both types require supporting that will preclude "drooping" or vibration to keep from moisture "pooling" in the line which will cause "slugging" of the output air.

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Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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I am relaying all of your suggestions to my husband who has been a Mack mechanic for over 30 years. I’ve never seen him stumped until this. 
Thanks again, I appreciate you guys!

my puppy’s got her pep back!😂

btw, I’m the driver and my hubs is the mechanic...it works for us😊

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On 4/16/2021 at 5:15 AM, Swishy said:

we have a mack th@ passes a bit of oil down to the 1st tank, the oil n heat carbonizes n clogs up the main pipe th@ restricts the air flow

This is also why it is so critical to use a proper coalescing air dryer cartridge on US07 and newer engines.  Too many people try to save a few dollars by using older style non-coalescing cartridges or not changing them on time (once per year).  Failing to maintain it risks not only clogging up the tanks, but screwing up your entire AHI system.  

 

From MTPI 561-016:

Note: Proper servicing of the air dryer with an oil coalescing media cartridge is critical to the
Aftertreatment Hydrocarbon Doser (HC Doser) system. The HC Doser system uses
compressed air to purge fuel from the HC Doser nozzle supply pipe and the HC Doser
nozzle. This air is also used to continuously cool the HC Doser nozzle and to prevent soot
from the exhaust entering the HC Doser nozzle. The removal of oil from the compressed air
system is critical to support the function of the air control solenoid valve in the HC Doser
dosing module. Oil in the air supply can collect in the valve and cause it to stick, inhibiting the
function of the valve. Additionally, oil in the air can collect on the HC Doser nozzle and form
deposits which can reduce HC Doser nozzle flow. Coalescing Air Dryer Cartridges should be
serviced and replace every 12 months during normal preventive maintenance.

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