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Help analyzing chirping noise from engine - **RESOLVED**

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MultipleMan

Probationary Member
13
1
Dec 19, 2011
Houston, Texas
I recently put my 98 GSX back together and am trying to figure out where this high pitched rhythmic noise is originating from. It doesn't appear when the car is cold started, but surfaces after some time driving. The noise is greatest at idle and goes away (or I can't hear it anymore LOL) by about 2500rpm. Seems to be coming from the timing belt side. Any ideas?


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The source seems to come from the timing side. I would check out the tension on each accessory belt, followed by taking the upper timing cover off to see on your if the sound gets louder.
You could adjust the tension one belt at a time to narrow down which one it is. I assume you have all new belts?
 
Thanks for the input. I did the timing belt and all accessory belts about 15K ago and haven't touched them since. There was no noise last time the car was driven which was about 6 months ago. So far I have tightened the power steering and alternator belts separately but the noise has come back each time. The tension on the AC belt seems fine but I will try tightening it down a bit more as well and removing the upper timing belt cover. FYI the noise doesn't change in character or intensity when I turn on/off the AC or the headlights. Revving the engine to 3K seems to make the noise go away (but I'm not 100% on that, could just be drowned out).
 
When you changed the belts, did you check the condition of the pulleys? spray some wd40 on the bearings of the pulleys and see if it goes away. Hopefully I'm wrong but it could be a pulley ready to give. Is there anything that you've noticed that changes when/if it goes away? Hows your power steering?
 
Ok small update. I pulled off the upper timing belt cover and tightened the AC belt a tad. I did a really detailed inspection of all the belts and surrounding area and I don't see any visual signs of rubbing. After firing it up again, the noise is the same. No change as far as I can tell. I turn on the headlights and radio, crank the AC on max, and turn the steering wheel lock to lock and it makes no apparent difference. I have not noticed any change in behavior of the car with the noise. Everything seems to be working perfectly as far as I can tell.

However upon further inspection, I hear the noise most clearly when I place my ear above the turbo compressor (see around :08-:10 in vid). Now it could be just sound bouncing around and playing tricks on me. But I am suspicious now because in the past few months I have replaced it along with the following mods:

Extreme PSI Hard Intake
PR FMIC
Newly rebuilt 16G with new compressor/turbine wheels and EVO III turbine housing and new actuator (purchased from Steve93Talon)
EVO III Exhaust Mani
EVO III O2 Housing
RRE 3" DP
RRE 3" High flow cat
Removed EGR block off plate
Replaced PCV valve


Any more ideas? Does anyone think this noise could be turbo related? I am still not ruling out anything at the moment. I guess the next step is to take a better look at the pulleys. I didn't notice anything wrong with them when I changed the belts. I don't see a good way to squirt the bearings with any lube so I guess I gotta pull some belts? Just trying to narrow things down as much as possible. Thanks


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Last edited:
Thought I'd post a followup report. I ended up replacing the alternator, AC tensioner pulley bearing, all accessory belts, timing belt, all related pulleys, water pump, and harmonic balancer. Thought that would fix it, but nope!

Went back to do some more internet sleuthing and someone with similar symptoms had diagnosed their problem as excessive crankcase pressure. So got the car warmed up and chirping, loosened up the oil cap and a huge vent of pressure blew out and the noise went away instantly! Ok, so why the abnormally high crankcase pressure? Turns out the breather port on the valve cover is completely clogged somehow. I can not blow or suck anything out of that hole. So tomorrow I am removing the baffles under the valve cover, unclogging whatever needs unclogging, and hopefully have this problem sorted out for good. I may have thrown $700 (whelp) worth of parts at my car needlessly, but I'm just glad I finally figured out what was going on. I was pretty damn close to throwing in the towel and just selling/junking the car :banghead:

TL;DR - Car starts up fine with no noise. After warming up, develops loud chirping noise that sounds like dying bearings/pulleys coming from the oil pan area. Turns out to be excessive crankcase pressure due to clogged breather port on valve cover.

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