Here is my situation. I have a 04 6mt with 44k on the odo.
I have the same loud embarrassing squeaking as most of you have. I live in Los Angeles so I don't have the extreme cold weather that some of you have. But everytime when I roll from stop, it squeals. Up to speed in crusing speed, like <40 mph, I let go the gas so I can hear, the noise is there whenever the car go over any size bumps.

Last time when the dealer did the Airbag recall, the tech indicated my belts show crack marks. I bought the OEM belts and changed them myself after following instructions from this forums. I tensioned them properly using the OTC tensioner. There are less and quieter noise. BUT the noise is still there.

I see some of you are talking about chaging the idle pulleys. Are you talking about the two adjustable ones bacause on the P/S belt, there is a fixed one at the top.

The car drives fine, it is just annoying and like some of you said, it is embarrasing.

 

It's defiantly the Idle pulley, two of my friends replaced it and the noise went away. I will buy the pulley and swap it out and update this thread it's pissing me off already i can't stand it.

 

I'm having this problem also. I recently changed the belts (both) on 2004 g35. The belts started squealing after the change. We've tightened them and tightened them hoping it would stop, nothing. The problem is it's only on a cold start and then goes away after a few seconds. If I stop and go in the gas station, etc for half hour or whatever then start, does NOT do it. But if I let it sit all day or all night and start after a few hours it squeals like crazy. NEVER did this before changing the belts. I also might add, it's been in the 90s here b/c it's summer so I know it's not b/c it's cold outside. Can anyone help with this?

 

I have replaced and removed pulleys. Since then, I have had NO squealing problems.

Replace both idler pulleys and remove the big pulley right next to the power steering pulley.

 

how much did the pulleys cost you?

 

I think they are about $80 each and are only available at the dealer.

 

Recently replaced both belts and idler pulley. Squeak went away after replacing the idler pulley, but now I have a squeak on cold starts. I'll try tightening the belts and see if that fixes it.

 

There is an interest thread where G35 owner experienced similar sqeeling issues during cold startup and disappearing a few seconds later. The answer, for me at least as well as him, is not because of cold weather. It is because of additional loads placed on the belts during startup after a while from being started. Namely the electrical discharge when the engine is off and not charging the battery. The alternator is creating that load and slipping. That is what a squeel is, it is the belt slipping either because the belt is not tight enough or there are contaminants on the pulleys, for me at least. Coolant was spilled over the pulleys a couple weeks ago and the belts replaced because of squeeling. The belts were in relatively good condition and I felt at least 10k more miles left on the belt. that was a misdiagnosis. The belts had to be removed and both the belts and pulleys needed to be CLEANED if you know that they are contaminated from oil, coolant, or grease. The belt with dishwashing soap like Dawn or in my case Method. and the pulleys needed to be cleaned with Brakleen and a toothbrush. After I did that the sqeeling all went away. Instead of replacing everything, nobody wants to clean because it is to beneath the mechanics to do so and not replace everything that already appears to be in good condition. If this squeel did not go away after replacing a pulley or belts and tightened enough, its because the other pulleys are contaminated too and need to be cleaned.Try it if you done everything else already and it still squeels when you start the engine cold.

 

I STRONGLY recommend buying one of those cheap Gates 91107 and 91132 belt tension gauges. They're under $20 usually and super easy to use, take the measurement at the longest section of belt, the G35 is very accessible on the top of the engine bay.

Adjust belt tension to the FSM specs:

New primary belt, 188-208 lbs
Used primary belt, 164-184 lbs

New AC belt, 106-126 lbs
Used AC belt, 78-98 lbs

Always make sure to make belt adjustments on a cold engine or let it sit for an hour to cool off before checking tension. If installing a NEW belt install it to new tension, run the engine for 5 minutes, then turn it off and check tension AGAIN and set to the NEW belt value again.

An improperly adjusted belt can cause a LOT of extra repairs, too much tension will absolutely eat the bearings off of all the pulleys or just shred the belt. Too little tension is obviously loud and annoying, generates a TON of friction heat and will scorch /wear the belt quickly.
Just like you use a torque wrench to tighten bolts you should always use a belt tension gauge to tighten belts, they won't squeal if tensioned within spec.