I would suspect there’s an issue with the timing belt tensioner. Also worth checking distributor bearing

 

I am leaning towards timing belt tensioner as well. I don't want to have to tear it down to fix it but I suppose it's much better than a transmission bearing! Do you know of any way to tell if it's the tensioner without taking the timing cover off?

Distributor bearing seems like comparatively low hanging fruit so I might go that avenue first depending on what I find with the stethoscope today. Previous owner swapped in a no-name aftermarket distributor so I would not be surprised.

 

Does it change when you turn the steering wheel? Then
change/flush the fluid take off the line coming back to the Reservoir, jack her up , you will have have someone steer lock to lock slowly to add Merc III to reservoir as you pump old stuff out,splint the hose with hose clamps on both sides of the splint forgot what hose size? and stop adding fluid when you see that it is mostly new fluid pumping out, the power steering fluid is mercon 3 atf I believe

 

This noise isn't power steering whine, it doesn't change when turning the steering wheel. More importantly, the noise I am talking about is present even with the accessory drive belt disconnected from the power steering pump (i.e., engine running but the pump is not).

Side Note: the Factory Service Manual (2004) calls for Genuine Nissan PSF, Dexron III, or Mercon in power steering applications.

 

Timing belt isn’t that big of a deal on this engine. Hardest part is getting the balancer off. Once you remove the covers you can put the balancer back on and run it without the covers and put your stethoscope directly on the tensioner. Water pump replacement would probably be recommended if you’re this deep anyway

 

Yep. And if you don't know when the last time the belt was changed it's worth doing. It could also be the water pump. Basically while it's apart I'd just buy the Gates timing and water pump kit and change them all out. I'd also do the crank and cam seals while you're in there, but I'm a "while I'm in there" kinda guy.

 

Also check to see if it’s a bearing in one of the two belt idler assemblies.

 

could be a alternator bearing or other pulley wheel, timing belt wheel, belt tensioner etc.

 

You're not reading the guys posts.

 

You could pull the distributor and turn it by hand since it's easy. You may not here the whine but may feel it depending on how bad it is. Luckily the only whine I hear in my Xterra is just my wife when she needs food or coffee and that's a usually easy fix.

 

I’ve also ruled out the Air Conditioner, Power Steering pump, Water Pump, and associated pulleys/tensioners by running the engine with the drive belts disconnected

 

I removed the Power steering/water pump belt and the AC compressor belt but not the alternator belt (had to button everything up because it was late and I had to get to work in the morning).

Last night I checked around with the stethoscope and wasn't able to pinpoint anything for sure. However, I feel pretty confident that it's not a transmission noise or the alternator as both were essentially silent with the stethoscope. I was able to detect a faint whining from when placing the stethoscope on the distributor housing but it was quiet enough that I don't think it's the cause.

Most likely, it is the timing belt tensioner. I can hear the whine when placing the stethoscope on the timing cover (about the same loudness as the distributor).

Unfortunately, I didn't get much farther as I discovered a decent sized coolant leak running down the transmission bell housing while I was crawling under the X! Looks like I'll be tabling the whine issue to replace the intake manifold gaskets for the second time in three years... lucky me! Guess that's what I get for buying cheap gaskets! Maybe I'll just do both while all the coolant is drained...

 

I removed the Power steering/water pump belt and the AC compressor belt but not the alternator belt (had to button everything up because it was late and I had to get to work in the morning).

Last night I checked around with the stethoscope and wasn't able to pinpoint anything for sure. However, I feel pretty confident that it's not a transmission noise or the alternator as both were essentially silent with the stethoscope. I was able to detect a faint whining from when placing the stethoscope on the distributor housing but it was quiet enough that I don't think it's the cause.

Most likely, it is the timing belt tensioner. I can hear the whine when placing the stethoscope on the timing cover (about the same loudness as the distributor).

Unfortunately, I didn't get much farther as I discovered a decent sized coolant leak running down the transmission bell housing while I was crawling under the X! Looks like I'll be tabling the whine issue to replace the intake manifold gaskets for the second time in three years... lucky me! Guess that's what I get for buying cheap gaskets! Maybe I'll just do both while all the coolant is drained...

Most likely there is a crack in the coolant fuel warming system, changing the intake gasket would just aggravate whatever is leaking more, only thing the gasket is going to do is stop an air leak at the intake ports. Lots of hoses to tweak and check in that coolant throttle body fuel warming system most likely those menagerie of hoses or the back two firewall in/out coolant hoses.. I just looped mine off at the firewall because it was a headache, but beware if you live or plan to drive in alot of cold weather, system is supposed to be for carb icing?. Distributor bearing is now my best guess.

 

The coolant to the plenum is indeed for warming the throttle body to prevent it from icing up in cold climates. It also is what heats the wax pellet in the Fast Idle Control. I deleted mine and bypassed the intake manifold all together, but I live in the tropics. The coldest weather I've seen here is about 67 F in the winter... at night... in the mountains... I wouldn't consider doing it in the continental US (maaaayyyyybeee Florida).

Don't forget that there are metal pipes that run under the lower plenum. It is not unheard of for the hoses they are attached to to leak. The ends/niples of those pipes are also prone to corrosion (I had to replace mine because of it). Any coolant leak in the lower plenum gasket or the pipes under the lower plenum end up in the middle of the top of the engine block between the heads. It then tends to drain backwards towards the bell housing, especially when you accelerate.

I believe that someone recently posted a thread on a leak back behind the bell housing. One of the freeze plugs appeared to be leaking.

 

Yes, I meant the FIC, not IACV! I'll be sure to inspect the hoses/hard lines under the plenum as well! I was young and dumb when I did this the first time and didn't replace any of those coolant hoses. Hopefully that's all it is so I don't have to mess with pulling the fuel rail and intake manifold. I saw that post as well about the freeze plugs. I guess we'll see!

 

Hmm I was gonna suggest something with the wax pellet, but yeah, on your original issue it sounds to me like you have a bad bearing in your tensioner or idler pulley.

I concur, crank/cam seals are easy to get to and worth doing when you're that far into the motor.

 

Update: So I finally got some time to work on the X today and decided to try to what @Blackberry suggested. I got the timing covers off, put the crank pulley back on, and started the engine. Using a stethoscope on the timing belt tensioner pulley nut, I was able to determine that it the tensioner was definitely the source of the whine! I had a new tensioner on hand to replace it and, this time, made sure I didn't over-tension the pulley. Ran it again and checked with a stethoscope and no more whine! Thanks again, everybody! Now to start on the coolant leak...

 

Well done. Always good to hear a success story. My mother in law used to say...everyone loves a happy ending.

 

Coolant leak ended up being the intake manifold gaskets. I noticed the bypass hose by the thermostat had started seeping as well so I replaced all the coolant hoses along with the intake manifold gaskets. Figured I might as well replace all the vacuum hoses as well since I was in there. Didn't have time to refill the coolant and take it for a drive but oh well, timing belt AND intake manifold gaskets in a day! I'm gonna be sore tomorrow! 😅