2nd Gen Non-Engine/Transmission sounds like rain behind the dash

[pdxkid]

When the truck is warmed up, driving on the highway (is when I usually notice it) it sounds like it is raining off in the distance, behind the dash, up by the cupholder and vent. It's making a kind of swooshing noise. This happens with the fan in the off position as well as on. Is this something to do with the heater core? Ideas?

 

[Adventure Bob]

Sounds like air trapped in the heater core or feed line. My grand does this and I havent taken the time to get it bled properly.

 

[GAmes]

Check your heater hoses carefully for a pin hole leak. When I fixed my leak the sound went away. Air bleeds out by way of a wobble valve on top of the thermostat housing through the very small hose that attaches to it.

 

[Allnew2Me]

Also check the AC drain, sometimes it can get clogged and the fan will toss water around. The drain is a rubber hose under the truck on the passenger side under the HVAC box with a flat molded into it. Stick a wire up there and see if you get water out of it.

 

[pdxkid]

thanks for the responses, when my back gets better, I'll start crawling around in there