Long time listener, occasional caller.

We have a 1998 Ford Expedition XLT 5.4L 4WD AT with about 154,000 miles on it. In Spring 2007, we had the AC clutch replaced by the dealer due to a squeeling sound. In September 2009, the AC compressor seized while driving back from Maine and the AC compressor, upper hose, drier, accumulator and similar were replaced by a shop. Looking back, we may have had some warning since there was a rattle sound from the lower front of the engine compartment and the AC system was starting to loose effectiveness. The compressor housing was visibly cracked when removed.

In May 2010, while driving back from Maine (again), we started to hear a low, but perceptible whirring sound from the compressor at speed. It is a different sound than before - before it was a rattle sound, now it's a low whir. Cycling the AC cycles (max AC, AC, defrost) makes it pretty clear that it's something on the AC side. The AC pumps out plenty of cold air, so I don't think it's low fluid. One thing that is unusual is that it takes running the car at speed for a while to get the symptoms to occur. On Monday, I drove the truck for about 40 minutes around town and could not get the problem to occur, but after about 10 minutes on the freeway, I could start to hear the sound. By the time I was close to the shop, it disappeared.

Any suggestions?
-Eric Benson



The

 

Most failures are from lack of freeon (as the freeon gets low the ability to carry oil thru the system decreases=compressor failure) As long as the COLD air keeps pumping and the cycle times remain about the same I would run this until something changes.

 

Try using a mechanic's stethescope on the A/C compressor. From your description you may have bearings going bad.