Looking for cooling fan operation pattern for 99 QX4

[bmlawless]

I have a 99 QX4 with the 3.3L engine. I am tracking down a noise and I noticed that my cooling fan is always turning. In the other vehicles I own, the fan is wither electric, or is turned by the belt but sits idle until a fan clutch engages it.

I looked at the service manuals that I have downloaded and it looks like the fan is connected right on to the end of the water pump shaft and there is now electro-magnetic clutch to activate the fan. In reading the literature, there is also no description of operation that mentions any time when a clutch may turn on or off.

From what I can see the fan is always on , but that doesn't make much sense. Is this right?
Modified by bmlawless at 8:07 AM 7/28/2008

[bmlawless]

Anyone? Maybe someone could just pop their hood when their engine is cold and the A/C is off and see if the fan is turning. Then kick the A/C on and see if the fan turns on.

[fueler]

nah man its supposed to turn 100% of the time ur right on the fan clutch.. but its not electro magnetic... its thermal viscous... its purely mechanical and stiffens up/loosens up depending on the temp at the fan clutch... theres fluid inside the clutch that does this

it (the fan clutch) loosens up at freeway speeds but still spins... it will always be blowing hard when youre at a standstill with the hood popped, no matter if the engine is cold or hot, no matter what the weather is like outside...

good luck on the noise... check to see if maybe a blade is hitting somewhere on the shroud? shroud is pretty flimsy and would be easy to knock loose. check the top and the bottom

[bmlawless]

Unfortunately, this corresponds directly to my A/C compressor. It starts shortly after I turn is on and stops the instant I hit the econ switch.

I am holding on to that little bit of hope that the extra load of the A/C compressor is straining something less expensive.

[fueler]

its probably the ac compressor itself... it always makes a little bit of extra noise when engaged.... and will quiet down when u press ECON...

[bmlawless]

I wouldn't call this a "little extra noise". I first knew something was up when some people crossed in front of me in a crosswalk and looked at the front of my rig with weird looks on their faces. I thought something must have been broken. I checked it out when I stopped and nothing was out of place.

A day or so later I noticed a vibration while I was stopped at a light. I figured it was the cooling fan. When the fan comes on in my pickup, you can really hear it. I thought it must be the same deal in the QX4.

Then I got gas and checked my transmission fluid. I reached in to start the car, opened the hood and this fantastic buzzing sound started. I turned off the A/C and it stopped. I waited a few minutes and turned it back on and after about 15 seconds, it came back.

The clearest description of the sound is a buzzing sound. It is very loud and can be easily heard from 50ft away. My first thought was the fan shroud too, especially when I found a loose bolt. I have since tightened it down and verified clearances. It only makes noise when the A/C is running, but not always. It will always stop instantly when the ECON or OFF buttons are hit.

Oh yeah, it only seems to do it at idle.

[SnowSurfLax]

It's your compressor! Mine does the same thing. Essentially, it's going to make that noise until it fails.

Does it sound louder when first started in the morning? Mine does. Then the noise gets quieter, but still there. Annoying, but not much you can do except have the compressor replaced. Probably cost you around $400 I think, since you have to get the compressor replaced and then get the AC recharged.

[fueler]

yea dont worry mine is loud as hell too. like a mechanical "TRRRRRRRR" sound... in the cabin u cant hear it with the windows closed but outside its pretty damn loud

I dont think itll fail on ya.... mine has always sounded like that