Having a small whistle only at full operating temp

Hey guys, running at 185k miles, 2013 RW, hearing a small whistle on the passenger front of the engine or directly in front of the engine behind the radiator. Already did the tensioner and pulley there, and also the idler pulley... Did an alternator and battery test, both are good. I was spinning the fan, and wasnt sure if its supposed to spin freely or not? It has some friction when i spin it clockwise or counter-clockwise. Wasn't sure if that's a common failure or not... could it be bearings in the alternator or something else?

Also have a the engine temp running a tad bit low all the time, guessing thermostat is stuck open.

 

Do you think it is coming off of the accessories running off of the serpentine belt or elsewhere.
“Usually”, a whistling type sound is common to a “vacuum” leak in the air intake tract. A vacuum leak typically also affects engine operation due to unmetered air entering the system.

 

Its more like an ongoing small squeal that isnt too loud, only can be heard when the windows are down when parked or at low speeds. where would i check for a vacuum leak

 

I can’t really help you with that. I know that on my LX450/80 Series LC, the rubber intake section from the air cleaner box to the intake/MAF was prone to cracking.
I just replaced the alt, belt, belt tensioner assy, and idler pulley on my Tundra. The alt had quit, and just a few weeks prior to it dying, I would occasionally hear a “metallic clanking” sound at start up. It didn’t last long (less than a minute), so I didn’t pay much attention. While I was “in there”, I decided to replace all that stuff as I had no idea when the PO or the orig owner had replaced any of that stuff. Upon inspection, the alt was noisy as well as the idler pulley.

 

We may have the same issue. I only hear it on the throttle, but not off.. I'm assuming it's the air intake tube or in my case the gasket at the throttle body as the last time I removed the intake throttle body I didn't replace that gasket.

 

My problem is also at idle only when its warm which is weirdddd

 

I don't think I have that same issue, but I would inspect that hard plastic intake tube....

 

I have a cold air intake, would that leak be on the intake manifold or the stock intake. I did notice when i pulled the engine cover off, and i was hearing a chug like a train from the intake manifold area... normal?

 

I would inspect that intake to be fully seated in its place. Check all vacuum hoses to it as well.

 

I would definitely start with the air intake.

I used to have a slight whistle (on throttle) and it turned out to be the K&N drop-in filter within the factory intake. Swapped to a regular paper filter and the whistle has never returned.

Some cut out the metal MAF protection screen inorder to stop the whistle while retaining their high flow, aftermarket filter elements.