How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask catmastertech Your Own Question
catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 2367
Experience:  19 years Cat, 3 years Case
Type Your Heavy Equipment Question Here...
catmastertech is online now
A new question is answered every 9 seconds

2000 Kenworth, Air compressor was working morning..governor

Customer Question

2000 Kenworth, Air compressor was working fine. Came home, shut it off and the next morning
all I can get is 30 lbs of pressure. Changed governor, no change. Not sure where to go from here. Maybe its the air dryer, but how can I tell?
Air compressor has almost 970,000 miles on it, but has been working good until the other day.
Submitted: 8 years ago.
Category: Heavy Equipment
Expert:  catmastertech replied 8 years ago.

Is it possible you have a large leak between the compressor and the tank? I would check the drains and sludge valves also. If you have a large leak you will not here it when you shutoff engine as pressure is gone as soon as engine stops.

Remove the tanks supply line from the compressor and hold your had agiast it with the engine running. You will not feel a lot of pressure but, you should feel some.

If you can connect shop air pressure to the system at this line, it is easier to find a large leak.

I also had a check valve at the first tank stick open and it would not let the tank pressurize.

Customer: replied 8 years ago.
Actually, I did air up the truck so I could move it,but I didn't notice any air leak sounds
after I shut it down. I had put about 90 psi in it before moving it.
Expert:  catmastertech replied 8 years ago.

If you add air to a secondary or dry tank another check valve will prevent air from leaking out the primary or wet tank.

You have two secondary tanks and that is the pressure you see on your gauges. The wet tank is not connected to any gauge. That is why you need to add air at the line from the compressor. This will check you whole air system and the dryer as well.

I have missed this step before and wasted a lot of time only to find the supply line broken in the frame were I could not see it.


Customer: replied 8 years ago.
I have a air valve on the govenor and that is where I added the air to the tanks.
I only have 2 air tanks but I will check for air leaks.
If it was the air dryer, how do you check for that?

Since I changed the govenor,there is air leaking around the top of it.
Right where the plastic cap screws on it at the top.
Does this indicate anything to you?

Expert:  catmastertech replied 8 years ago.

Governors have several plugs that need to be added or moved.

If you still have the old governor double check the location of the plugs so you don't have any in the wrong place.

Make sure you did not cross the line from the wet tank with the line from the dryer.

The tanks have a weld in baffle that seals the sections. You can tell it has two sections by counting the drains on the tanks. My truck is a single tank with three sections.

Customer: replied 8 years ago.
Donnie,we sprayed soapy water on every line we could find.
Found no air leaks.
By passed the air dryer by removing the airlines and connecting
them together, Truck aired up.

It was a bad air dryer!
Expert:  catmastertech replied 8 years ago.
Glad you found the problem, I guess the dryer is stopped up. I am sure that is cheaper to fix than the air compressor.