What�s up guys, I have a 2006 G35x with about 101k on it. I�ve been experiencing some rattling and chirping sounds at idle. I replaced the belts with OEM 2 years ago and tried tightening them but that didn�t fix the sounds. I also replaced both tensioner pulleys yesterday because they were old and seemed to make noise when I spun them with the belt off. I figured that this would solve my chirping and rattle at idle but it didn�t.

I have not replaced the 3rd idler pulley or done the delete yet because I wanted some more opinions. In one linked video you can hear the chirping sound at idle and the other has a rattling noise near the compressor. This compressor rattle went away when I clicked off and cut the air off and it�s intermittent at idle, it comes and goes.

The belt/pulley noise has been there since it started getting colder here and I�m stuck. I tightened the belts today and they�re snug and not super old. I get a little chirp on cold starts when turning the wheel out of my driveway as well. Any driving or increase in rpm at idle makes all sounds disappear. Do these two videos sound related, any ideas as to what the noise is that I�m hearing? Thank you so much.





 

Take the belts off and spin each of the accessory/idle pulleys by hand. Also wiggle up/down/left/right/in/out to check for play indicating something is worn out.

The tensioner pulleys when you spin them by hand they should only make 1/2 to one full revolution. If they spin very freely or have ANY noise when you spin them they need to be replaced.

Use a belt tension gauge (krikit gauge) to get correct tension on the belts rather then just guessing, squeal/chirp on startup is indicative of wrong belt tension. Too much tension and you will destroy the bearings on the pulleys.

You check tension on the primary belt at the top between the power steering and idler pulley, 200 lbs for a new belt, 175 for a used belt. If you want to measure belt deflection instead it's 4mm new and 5mm used measured from the same location with 22 lbs applied force.

You check tension on the AC belt at the top between the crank pulley and the AC compressor, 125 lbs for a new belt, 100 lbs for a used belt. If you want to measure belt deflection instead it's 8 mm new, 9 mm used measured from the same location with 22 lbs applied force

 

Thanks for the reply Cleric. I already replaced the 2 tensioner pulleys the other day so they can�t be what�s making the noise. They were my first guess since they seemed rusted and old when I replaced them.

The only idler pulley left is the unnecessary fan pulley on the PS/ALT side. I could do the pulley delete with 2 new belts but they probably only have 15k on them. Is that 3rd idler one that commonly goes bad on G�s? I suppose I�ll have to check the rest of the pulleys again but nothing stood out to me the other day when I was inspecting them. It seems that people have not really had problems with the PS pulley or Alt from looking through this site.

I tried measuring the deflection of the PS/Alt belt and it seems that I�m getting around 6ish mm of deflection but it is really tough to read in that tight space. If I put some force on it I could get it to 7mm I bet but 22lb of force doesn�t sound like much.

 

Yeah 22 lbs really isn't that much. It could literally be ANY of your pulleys that are making the noise so I would just remove the belt and spin everything by hand and give a pull/tug test on everything. I wouldn't say that any of them were more prone to failure than any other one. The PS, AC, alternator, are more robust with their bearings so they would be the least likely.

Usually if it's making noise with the engine running it's VERY obvious which one is the problem when you spin them all by hand.

 

Alright I�ll try to spin and pull them again, the other day every pulley seemed fine except maybe the tensioners. Any chance that chirping sound in my video could come from the belt being glazed or not tight enough? I tried tightening it again but I�m wondering if it�s not a pulley as the extra idler is the only one left. Thank you Cleric

 

It could definitely be that idler but you need to troubleshoot by spinning everything by hand so you aren't wasting time/money on parts that aren't fixing the problem.

Also use a flashlight and see if there's any accumulation of rubber/gunk in the pulley grooves, it's extremely uncommon except on vehicles where the belt is allowed to just sit and squeal for a VERY long time. If there is buildup you can use a wire brush (not the little toothbrush sized one but the bigger wire brush like what welders use is much easier, definitely not a wire brush on a drill or power tool) to clean the pulley grooves. I doubt that's your issue though it's usually a persistent belt squeal that won't go away even with proper tension, but you did mention you have a belt chirp on startup.

Btw that idler can sometimes be an absolute bitch to remove, have a small screwdriver-sized prybar handy. It's easier on the non-revup engines but if you have a revup you're going to be prying to get that thing out since it's pinched behind other stuff. Will also likely need to use a hammer/drift to get it back into position. The non-rev it's not pinched behind the cover so it's a LOT easier to remove.

 

I took my belt off again today and spun the pulleys by hand as you suggested. The power steering, alternator, and new tensioner pulley did not rotate very much but the 3rd unnecessary idler spun a lot. I linked a video down below, it spun the most but made no noise. I�m guessing that this is normal but do you know if that idler should be hard to spin as well?

The only noise that I could hear was from the new idler pulley and it seemed to be coming from the old rusted dust shield in front. I took it off and it definitely was not the pulley itself, but the shield/washer that are in front of it.

If the 3rd idler I show spinning in the video is normal, maybe it�s the dust shield making all this chirping/rattling noise on the pulley? Let me know what you think, thank you.

 

That third idler shouldn't spin that freely, go down to a parts house and have them pull a new one so you can compare.

 

I just did the idler pulley delete today and it did sound like there was a bit of a noise when spinning it when it was off. The other 2 idlers that I replaced also sounded like the bearings rattle when spinning by hand. I believe I might have heard a slight rattle after I put the new belt on and tightened everything up. However, this was not a real cold start so I cannot be certain yet. I spun the remaining pulleys and tugged them for any movement play.

I noticed that the P/S pulley can move slightly back and forward if I tug on it. However, there is no side to side or up and down play. Just a back and forth if I pull then push. I can spin it as fast as I can and hear absolutely no rattling or noise from the pulley either.

I attached a video below, is this very slight amount of movement anything to be concerned about? Thank you for your help. It may have sounded better without the 3rd idler but I�ll need a real cold start tomorrow to know.

 

That much end play on a power steering pump is fine, it's a splined shaft that has a pilot bushing at the rear of the casing. I typically don't worry too much about end play on them until you're getting close to 1/4" because at that point you start running the risk of disengaging the shaft from the pilot bushing.

The belt keeps it centered though, so it's not like it's going to be showing that end play while it's actually being driven by the belt.