The original A/C compressor on my 1998 F250 bit the dust early Summer last year. Took the truck to a local mechanic shop. I was told the clutch was severely burned up and they recommended replacement of the unit, as well as the other usual parts in this scenario.
Once the new unit was in, cooled like new, but now I heard an odd swooshing sound. Took the truck back for them to check. I was told, since the new noise happens whether the A/C is on or off, it was something unrelated to the new unit. All I know is the new noise was not there until after the new A/C compressor was installed. The noise lasts about 3 seconds after the engine is shut off, and gradually tapers off to nothing. Sounds to me like the A/C compressor, whether the clutch is engaged or not, is making that noise, and it bleeds down once the engine is turned off. The replacement parts and labor cost me over $800, and the last thing I need is for this to lead to premature wear and eventual death of the compressor.
Has anyone else out there encountered this kind of issue with a new replacement A/C compressor? The shop claimed the first one they tried did not fit, and they had to search a while to find the "right" one. The 1998 is a great truck, but I have had several instances of parts not being correct...first year of the redesigned F250...
I replaced the water pump right before the compressor replacement...did not have the tools to do that A/C work...
I am thinking I will take the belt off and run the motor to see if the noise goes away, then take it from there. Any suggestions would be most appreciated.

 

The noise you are hearing at shut-down is probably due to the AC system pressures equalizing through the orifice tube.

If so, it's harmless.

 

Thanks for the reply.
Why would the replacement make that noise when the OEM compressor did not? Could it be the replacment is after market and not built the same as the original? Guess I am being **** on this...the sucker cools like nobody's business...just loud as hell.

 

You reference at shut-down, not when running. Should I be hearing that loud "swoosh" when the engine is running, too, because it is a constant noise, only stopping once the motor is off.

 

If it does it while the engine is running and no AC on, then it sounds like it is low on coolant and you are hearing coolant flow through the heater core. You said you just did a water pump. You might not have gotten all the air out of the cooling system. Check your coolant level for sure first. Otherwise I would have to guess a vacuum leak.

 

Decided to give the truck a few weeks before getting back on this thread. The coolant level is fine. I have noticed the shwooshing noise is still there after the engine shuts off and is the compressor equalizing pressure. What I notice now is a definite whining noise that seems tied to the rpm of the engine up to about 2nd or 3rd gear when moving slow. If I turn off the A/C, the noise goes away, leading me to discount any tranny problems; the tranny has been working fine in the past and present. This whine sounds loudest at the low end of the center of the dashboard, right where a lot of the mechanicals are for the A/C and heater controls are. Late last year, I replaced one of the vacuum motors that controlled the upper door for the dash. I am wondering if one of the others or something related to that type of part is making this noise. Has anyone had this happen to them? This is a first for me.