Air Pressure High

[mdemars03]

So driving my M923A2 home from work I noticed the air pressure seemed to be higher then normal at just over 130 pounds. I also noticed on shutdown I have an air leak from a line going into the air governor. The leak was substantial enough to cause a drop in air pressure at idle. When driving down the road at about 1800 rpm though my air pressure was higher then normal on both primary and secondary air systems.

Since I have owned this truck normal pressure is right at 120 psi.

I know the drop in pressure is going to be from the leaking air line which will be fixed before driving again. Could the high air pressure be a failing governor or could the air leak be causing issues for the governor to create a high air pressure when at higher rpm, or am I troubleshooting the wrong spot all together for the high air pressure problem?

The secondary air system is where I see the biggest drop in air pressure at idle but it is also noticeable on the primary air gauge as well.

Trying to get input here so if it is more then just an air line leak I can get the parts needed and fix everything at one shot. I hate to be down for the same thing multiple times.

During all of this the brakes still worked flawlessly as the pressure drop never got below 95 pounds, but 95 pounds is too low for proper and safe operation in my personal opinion.

 

[simp5782]

I think we all would say fix the air leak first and see if the pressure goes back to normal before trying to troubleshoot something that may not be wrong at all. One step at a time

 

[mdemars03]

Just curious as my expirence with air systems is limited. How would an air leak cause high pressure at highway rpm? I will follow your advice and fix the leak first definitly and see what happens from there, but I'm just curious how high pressure at higher then idle rpm would make the air pressure go up with an air leak. My air system knowledge is limited and I'm just trying to learn here at this point.

 

[dmetalmiki]

Regulated air can (then) shut of the compressor by the sensor line allowing the compressor to "stall" (stop building air) usually by way of the valves. An air leak prevents this build up of 'sensing' air.

 

[The HUlk]

Regulated air can (then) shut of the compressor by the sensor line allowing the compressor to "stall" (stop building air) usually by way of the valves. An air leak prevents this build up of 'sensing' air.

Correct. The air governor detects the system pressure level. When the level reaches 120psi the governor sends air to the unloder valve on the top of the compressor causing it to stop feeding air into the system. If air to the governor is incorrect it would stand to reason this would cause incorrect system pressure. I learned a lot about the air system by working through some problems I had which are documented here...

http://www.steelsoldiers.com/showthread.php?141256-M939-Inconsistent-air-pressure&highlight=

 

[mdemars03]

Awesome. Thanks for the insight here and helping me better understand the air system.