Loud Fan Noise at start up and when AC is turned on

[maurus]

Since I just bought my 2011 QX56 used with over 90K miles on it, I am not sure if this is normal. Hope you guys can shed some light on this.

These may be 3 separate issues (or they may not be issues at all).

3 scenarios:

1. In the morning, when the engine is cold, when I turn on the engine, it makes a loud noise - sounds like it is the fan, not the engine. After about 5 to 10 seconds, it quiet down. Needle stays at around 1K RPM during the whole process, it doesn't go up or down. AC is not turned on at this time.

2. When I turn on the AC, the fan (not the AC fan in the interior of the truck, but the big fan under the hood) noise goes up and down in a regular pattern. It will get louder and louder and it will peak, then it will get softer and softer and quiet down and the cycle repeats itself over and over. This is when the truck is stationary. I don't know if it does the same thing while I am driving, can't really hear it while driving.

3. I've had the car for about 2 weeks and I did not notice this until today: when I approach a stop sign and come to a complete stop, when I gently step on the gas, I can hear the fan spins up and it gets pretty loud. It happened a couple of times today when I step on the gas paddle from a complete stop. As I mentioned, I have never noticed it does this during the 2 weeks I have owned it until today. It's not a particularly hot day or anything.

Does any of the above sound abnormal? If so, what could be wrong with it? I plan to take it in for the timing chain recall in the next couple of weeks, so I'd raise this up with the service folks at the dealership as well.

Thanks for any info.

[marctronixx]

you have a big huge engine. there is a huge fan that has a clutch. it is turned by the engine rpms.

it sounds like a MAC truck right? RROOOOOAAAAARRRRRRRRRRR... yes?

I LOVE that sound! :p

this is entirely normal.

the engine room can get heat build up over time and when you turn the engine over the fan will kick on and flush the engine room with cooler ambient air.

i see this several times here in the heat of LA, and you are experiencing normal activity.

by the by,

it will ramp up even without the AC on! if you are in stop and go traffic and its hella hot out, it can kick in....

[smola]

Its normal, mine does it too