Air compressor overhaul or replace

If the air is building then I don't think it is your air compressor. More than likely it is a valve that is not closing or something else causing the problem. The air governor is usually located near the air compressor. Once you start your truck you might want to have your hood raised and start listening and feeling for an air leak. Another thing to check around the air compressor is a pressure release valve. It should be located on the side of your air compressor. I doubt that is the problem. Once the valve releases it will need to be replaced. Air can be slow to build and have a problem sustaining air up to where it should. These valves will usually release air prior to fully building and continue to release. If your air is holding, then I don't think this is your problem, either. There should be pressure release valves on your air tanks. There could be some grit or dirt collecting around the valve keeping it open. I would also check the air dryer. Hold your hand underneath the dryer and see if you can feel air leaking. You could have a faulty valve, dirty filter or some dirt or grit keeping the valve from closing. I would first start with the air governor. I prefer starting with the least expensive repair first and work my way up from there. I have paid from about $10-22 for an air governor. You can do it yourself in a few minutes.

 

You can take the main line out of compressor off start truck and see how much it is pumping. Air governor is easy to change and cheap, any truck stop with a shop will have one, there are only a few types, one big and one small, they have a little piston in them that slides back and forth and it can stick.

 

It is easy to change out. Look around your compressor. It should be about 6" long and is bolted to the side of the engine or compressor. It is pretty easy to spot. When you change it out there are screws that come with the new governor. Make sure you put the screws in exactly like the old governor. If you don't it won't work properly. The screws control air flow. You may be able to google to find a photo.

 

I just googled "air governor" and a photo came up. It might help you find it on your truck. I was not able to copy it into a post.

 

You should just go to a cummins dealer and have them do the work. It is better to have them troubleshoot the problem and fix it than to screw around trying to figure out what's what.

You also may have a bad air dryer, I think Cummins used some sort of secondary pressure line from the governor to trip the air dryer valve on some ISX engines.

 

Try the governor and unloader valve first off. If it's building pressure when warm, and isn't leaking coolant, leave the compressor alone.
Those two parts should run you maybe $100, and will take about 20 minutes a piece to replace, if that.

Martin

 

The unloading valve could be an internal valve that is controlled by the governor which means that the compressor has to be pulled to fix it.