01 2500HD "Growling"

OK, so I am apparently in the "fixing" mode on my 01 2500HD P/U. I recently had my mechanic friend replace my engine oil cooling lines and recharge my A/C system in preparation for this summer.

Now, when I first turn on the blower system (Still heat right now), I am hearing a nasty "Growling" sound that appears to be under the hood; but could be under the dash area. The first time it did it (Yesterday), it "Growled" for ~2-5sec then stopped for ~8-10sec then did it again for another 2-5sec. Then never did it again. I shut the system off and back on and it wouldn't do it again (the truck was warm by this point). Then this morning when I got in to head to work, I started with the system turned off. Started the truck and idled for a few minutes before turning on the heater system. When I did turn it on, I heard the "growl" for ~2-5secs once and it didn't do it again.

I am wondering if there might be an automatic vent that closes when the system is off and for some reason out of the blue the mechanism is grinding. Any ideas what it could be and what I should go look for.

Thanks...:banghead:

OK, so I am apparently in the "fixing" mode on my 01 2500HD P/U. I recently had my mechanic friend replace my engine oil cooling lines and recharge my A/C system in preparation for this summer.

Now, when I first turn on the blower system (Still heat right now), I am hearing a nasty "Growling" sound that appears to be under the hood; but could be under the dash area. The first time it did it (Yesterday), it "Growled" for ~2-5sec then stopped for ~8-10sec then did it again for another 2-5sec. Then never did it again. I shut the system off and back on and it wouldn't do it again (the truck was warm by this point). Then this morning when I got in to head to work, I started with the system turned off. Started the truck and idled for a few minutes before turning on the heater system. When I did turn it on, I heard the "growl" for ~2-5secs once and it didn't do it again.

I am wondering if there might be an automatic vent that closes when the system is off and for some reason out of the blue the mechanism is grinding. Any ideas what it could be and what I should go look for.

Thanks...:banghead:

HVAC blower fan motors will make these sounds. sometimes intermittent ..as the motor gets worse it will always make this sound. you could remove the motor and oil the bearing a little to see if it goes away for a while . if so then replace.