01 Expedition "Air Comp"won't engage

mikedcf · 12-26-2007, 05:49 PM

Have a 01 Expedition that has air compressor for rear suspenssion. Problem is compressor won't engage. It usually starts up when I start the engine and levels the truck. I've noticed that it's been slow in responding of late. Any way to check this? Thanks!

ABE · 12-26-2007, 06:44 PM

If your vehicle has air springs for the rear suspension, there should be a sophisticated set-up. If your system is similar to the Lincoln Town Car (or other Panthers) there is a control module that governs the compressor based upon input from sensors. One is the door ajar sensor, so that the compressor will not run if it thinks the door is open (and therefore someone may be entering or leaving the vehicle). There would be a height sensor that dictates when the compressor is required to raise or lower the car; is your ride height too low?

There should be a switch to power the system off, and a relay and fuses to allow the compressor to operate. Check the fuses and relay's. The compressor itself should have a drier to dry the air in the system and prevent ice blocking pressure relief solenoids. If the drier silicate is full of water it will block air flow and the compressor will not operate. The drier can be removed and the silicate put in an oven for 30 minutes to dry it out and then replaced. The compressor itself has a bushing on the shaft that is prone to degrade and overload the motor. I have heard of one person who replaced the bushing with a roller bearing to fix such a problem, otherwise the compressor may have to be replaced.

Hope this helps.

mikedcf · 12-26-2007, 06:46 PM

I also forgot to mention the air suspension exhibits a slow air leak and/or overnight bleed down of the air suspension. Is this normal?

mikedcf · 12-26-2007, 06:54 PM

Yes, it does ride low at times. When left over night, the system bleeds down completly...but not all the time. I'll check releys and fuses. Thanks

ABE · 12-26-2007, 07:41 PM

No, the system must not lose any air at all ever. Sometimes the computer will release air, but no leaks. The most probable problem is leaking springs which age and crack, but a 2001 vehicle should not have this problem. Spray the springs, solenoids and hoses with soapy water to look for air leaks. You may have a failed solenoid at the top of the spring or a hose burnt by the exhaust or rubbed through.

The leaking components will wear out your compressor very quickly, so do not delay in finding the leak. You can get kits to replace the springs, solenoids and compressor. I will see if I can find some sites.

Hope this helps.