Primary air tank won't build air

[jesse20]

The air on my 2011 prostar with a 2009 cm871 builds up air slowly SOMETIMES, this just started on tuesday no audible air leaks, bendix governor and air dryer were replaced, and same thing is still happening, the 1st tank looses air slowly while idling with and without load the air lines were checked from the compressor to the governor and they are not clogged up I did a DPF tune up but I only cleaned the components and only replaced the exhaust back pressure sensor about 7,000 miles ago. The secondary air tank holds its air between 100 to 120 psi at idle, when the primary tank detects around 65 psi it will build up SOMETIMES, and other times I have to rev up the engine to get it to build at 120 psi, and sometimes it just won't build past 85 psi on both tanks. PLEASE HELP thanks. The pictures shows how my compressor looked when i did my EGR tune up.

[Rawze]

Air compressor average lifespan is only 800k miles. I replaced mine at 800k miles because it was sounding a bit noisy and didn't want to be on the side of the road unexpectedly. i also changed out the entire air dryer unit because they would not warranty the air compressor unless I did so.

[jesse20]

(06-16-2016 )Rawze Wrote:  Air compressor average lifespan is only 800k miles. I replaced mine at 800k miles because it was sounding a bit noisy and didn't want to be on the side of the road unexpectedly. i also changed out the entire air dryer unit because they would not warranty the air compressor unless I did so.

my truck has 526,000 how can you tell if the compressor is bad? I don't know how the compressor should sound, if its bad would it stop pumping completly?

[iRonin]

Fill up a spray bottle with soapy water and go spray all fittings, plugs/drain plugs around your primary tank. You might have big leak somewhere there, cause as you said your 2nd tank keeps 120 psi. Find quiet place, Build the pressure as much as possible shut ur engine, go outside spray and listen. You'll find it... Go by an air lines comming out of ur primary tank if nothing found at the tank. Spray them all the way to next fittings. Sounds like it leaks badly.

The oily spot under compressor has nothing to do with compressor. If you check more thoroughly, you find this oil comes from the top part of front gear cover. Might be leaky front camshaft seal, I suppose. Don't know exactly. Rawze, Gearhead or Uni can say what it is for sure. I have the same oily spot last 100K miles and it doesn't go any more. But my engine has 800K on it already.

[arch stanton]

I think it is the hot line leaving the compressor it is the braided steel line,spray with soapy water,they get old and brittle all is good until it gets moved.

Thats my guess

[uncleal13]

That braided line coming off the compressor to the air dryer can get a build up of carbon in it over time, enough to block it off or at least restrict the flow. If may need to be replaced.

[Rawze]

I had a bad leak on the solenoid block in the frame next to the transmission that would only leak until it got down to 90 psi once. The entire solenoid block backplane was cracked.

[in2trux]

Sounds like the compressor itself, sticky unloader. You could try wd40 in the intake of the compressor but you have to open the intake line at the compressor head.
I would also check the purge valve on the drier while it's building air. I've had them stick open and not be able to build air. Leveler valves for the airbags can also bleed off allot of air but they should be on the secondary.

[Waterloo]

Im thinking soot build up in the lines along with the unloader like in2 stated. Another thing, there is a head kit for these compressors, as the unit itself rarely fails. So don't get talked into replacing the entire compressor if that is the issue. The head kit is roughly $500 and is something you can do yourself. But, I would still get a spray bottle and spray, spray, spray. I'm always chasing leaks on my ProStar. You think it is fixed and another pops up.