Ok, my 1998 Expy with 4.6 and 150k miles now has another problem. I tell you, it never ends for me and my vehicles. Last week, the 4x4 quit working and approx. $850, two speed sensors, and shift motor, the 4x4 works again. I still have a slight whine when driving (not engine) I did not have, or at least did not notice before, but I have 4x4 again.

Now, there is a shoosing/hissing noise from under the dash. If the climate control switch is in any position besides off, the noise goes away. If you put the selector switch in the "OFF" position, the noise is there, and loud. You move the switch just barely away from "OFF", towards either of the two positions on either side of "OFF", and the noise starts to go away. I am thinking this is a vacuum problem but who knows?

Could it be a vacuum line leaking or come off?

Could it be the actual climate control unit went bad?

The a/c and heat still work just fine. All switch positions work fine, going from dash to floor, etc., etc.

Thanks for the input. My wife is driving it to the dealership as I type this for a diagnosis, but not to be fixed today, unless it is a hose or something simple like that. I wonder what they will tell her: $500 to fix it, probably.

Thanks.

Andrew

 

the hissing noise is more likely a leak in the vacumme system that operates the vac. pods that control the doors in the ac ducts.if thay were diagnosing the 4x4 system they could of been in the dash and pulled somthing loose.as for the whine,you could have a bad pinion bearing in the rearend.this is my thoughts to what i see in the dealership.good luck and let us know what they find.