Air compressor problem

I've seen compressors with their own intake and filter and I've seen them with the intake plumbed in between the truck's air filter and turbo but I've never seen it on the boost side of the turbo. Not doubting you at all GrapeApe, just found that interesting.

 

On your air compressor. What kind of compressor is it? You can get unloaded kits for most compressors. The BA921 compressors had an issue with oil coking up in them and causing slow air building because it's keep the valves from sealing good. The Tu-Flows generally causes excessive air dryer purging with they leak, I haven't seen many of those stick the valves open.

 

release brakes and pump brakes down to below 90 psi, say 50 or so and see if it will not build air pressure up on its own without raising the engine rpms. If it will not I would suspect the air compressor governor.

 

If it's a early isx,check the breather line for soot or if you've blown a turbo on what ever motor. On my n14 it has a little foam filter in the line,yours may have something like that,could be plugged up.

 

Your lucky to have a mechanic like that, their one in a million.

 

I'm surprised. Most older S60's pull air right from the manifold, very common for that hose to blow and drivers complain of low power. All of our 379 Pete's with Cat's up to 2007 all pull air from the intake. Actually I've seen more plumbed to the intake manifold than from an air cleaner. That's why air dryers have a turbo cutoff valve, so boost doesn't blow through the dryer when the compressor unloads.

 

Honestly the only one's I've ever bothered to look at closely (I haven't turned a wrench on a truck in over 5 years now since I went over to heavy equipment) were the 2006 14L Series 60's in Western Stars. The ones that company ran got their air from the intake pipe near the air filters.

 

Yup, they had the BA single cylinder compressors plumbed to the air box with that reed valve inline that used to always blow gaskets making a popping noise when the compressor unloaded. That started that with EGR. Before that, they used Tu-flow compressors, the inlet was only about a foot long and went to the bottom of the intake manifold. EGR putting soot into the intake manifold made everyone rethink using boost pressure to feed the air compressor.