A/C hissin’

[jflip]

2000 XLT 5.4- hissing noise located at rear left panel, seems to be coming from a small square metal box. I seem to hear the compressor turn on, then hissing, then the compressor cycles off, no hissing, and repeats over and over when I have my ac on.

I read that this may indicate low refrigerant, but any other insight?

FYI I have the crossover antifreeze spew happening on top of 1-4 coils/plugs/boots. I changed 1-4 plugs and cleaned the boots, and I believe bought time until the next fouling! Paid $1100 for all 8 plugs/coil/boots 8 years ago. Never again. Long term fix is to replace the intake manifold cover, right?

 

[riphip]

I am sure you meant rt rear panel. That would be the expansion valve hissing. It may be an indication of low refrigerant BUT you need gauges hooked up first to be sure.
The hissing is: High pressure liquid refrigerant going thru the valve, becoming low pressure gas feeding into the evaporator core, drawing heat from the air that the fan is pushing across the evaporator fins, blowing cool air out the vents. The gas is being sucked/pumped back to the compressor where the process continues. Small tubing is high pressure, larger tubing is low pressure.

I cannot hear mine but your hearing is probably a lot better than mine also.

 

[johnboneske]

When it hisses it is a sign of low refrigerant. My old Expedition did it when it needed recharged. I used to have to recharge it every year. Damn POS... Yes I an a AC tech, so I would always pull a vacuum and recharge it.