No air @ air drain valve on MCI 8

[chart1]

I was trying to run a air impact off the fitting at the air drain valve in the engine compartment on a MCI 8 and it was working fine then no air at all. went inside air gauge was at 110psi but no air at valve . No, air valve was not shut off, air was coming out fine 30 sec earlier.

[buswarrior]

Only should be air at the discharge muffler drain in the engine room when compressor is pumping.

Easiest to take your feed off the auxiliary tank under the driver, and less water through your tools.

happy coaching!
buswarrior

[JohnEd]

You need to take the air from the top of the tank.  Rust and crud in the bottom fouls the outlet.  Before you quit first bleed down the pressure and then push a wire up through the valve.  If you don't the "water draining" function may not work either.

John

[chart1]

My drain line comes off the bottom of a little filter about a foot back from the compressor in the engine compartment on the passanger side. So where is the best and easiest place to put a valve with a air nipple for a air hose?

[buswarrior]

 

Bottom of the auxiliary tank under the driver?

Or, you can find somewhere up higher...

happy coaching!
buswarrior

[gus]

As already posted, there is no air at the engine unless the comp is running and then it pulsates wildly.

This is because the check valve to the comp is after the water drain/muffler on the air comp outlet line.

Made the same mistake myself - live and learn!

[chart1]

Duh!! Now I feel stupid..Of course I don't have air back there. The gauge says 110psi. The compressor is not pumping. Like you said live and learn.

[luvrbus]

That must be a GM and MCI thing for the Jello bags the Eagles have a chuck up front from the factory they carry the same pressure as the rear tanks and compressor you can tap anywhere


good luck

[bevans6]

It's just a "where is that tap, anyway" thing.  On MCI's there is a (stock anyway) schrader valve on the ping tank, aka discharge muffler.  That is directly connected to the compressor and is in the line up to the air dryer.  If the compressor is running, it has compressor air directly which as said with little or no tank to buffer will be pretty variable.  When the air system reaches the compressor cut-off point, the governor tells the compressor to cut-off and tells the air dryer to vent.  When the air dryer vents, all of the air inside the air dryer vents including the air in the line back to the ping tank and the compressor itself.  The vent on the air dryer stays open until it's told to close by the governor when the next cut-in cycle starts.  Now - if you turn the engine off while the compressor is in a pressurization cycle, the vent on the air dryer is closed.  In that case there will be pressurize air inside the air dryer and the ping tank so you can find pressurized air at the ping tank when the engine is not running.  In cold weather it's good practice to stop the engine while the compressor is compressing so that  the vent on the air dryer is closed, so that it can't freeze open and leave you stranded in the morning.

Brian