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07-30-2009
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#1 |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,708
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Diagnosis for Whistling noise
While driving Tuesday, I noticed a high pitched whistling noise during the times I was idling and/or sitting at a light. Did not change pitch with engine rpm and was not present when cruising. Closed throttle is when it is at its loudest. I pulled apart air horn/throttle body and spotted what I thought were telltale signs of an air leak on the gaskets. Installed new gaskets, buttoned every thing up and started car. Same whistle. Difficult to locate as it almost seems to be coming from everywhere. However it does appear to be more pronounced towards the front of the motor. Anybody else ever run into this. Car appears to idle and run fine. I still suspect a vacuum leak of some sort.
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07-30-2009
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#2 |
 
Join Date: Dec 2003
Location: Chicagoland,IL
Posts: 2,679
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Re: Diagnosis for Whistling noise
Sounds like a vacuum leak.
Had one thru the plenum gasket it sounded like a supercharger. Pete
__________________
'91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage |
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07-30-2009
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#3 |
Join Date: Oct 2004
Location: Folsom CA
Posts: 1,654
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Re: Diagnosis for Whistling noise
Generally speaking, a leak big enough to hear will usually fubar the idle.
However, maybe in this case it don't for some strange reason. A really nifty "Grease Monkey - Old Timer Trick Quick and Dirty Vacuum Leak Test" is to use a portable propane bottle and spray UNLIT propane in the general area where the noise comes from while the car is idling. When the idle goes up, you've pinpointed your leak. Good luck!!! TomC "Crabs"
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TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B] |
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07-30-2009
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#4 | |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,708
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Re: Diagnosis for Whistling noise
Quote:
Just spoke with Al. Certainly sounds that way. He suggested using a spray bottle and spray the gasket area. See if I can hear a "gurgling" sound. Tom, I used to use the propane bottle on my Xfire. Another notorious intake for vacuum leaks. Sometimes I feel like jumped from the frying pan and into the fire. 
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07-30-2009
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#5 |
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Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,708
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Re: Diagnosis for Whistling noise
OK. Got it. Very unusual since this was a problem that was very easy fix. That's not supposed to happen with ZR-1s. Practically anything must require a "pulling of the plenum".
It was the release valve at the bottom of my "oil catch can". It is now PLUGGED!  
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07-30-2009
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#6 | |
   
Join Date: May 2007
Location: Peoria, AZ
Posts: 9,155
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Re: Diagnosis for Whistling noise
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I love the easy fixes. Nice catch Dom
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GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director  91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V |
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07-30-2009
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#7 | |
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Join Date: Dec 2003
Location: Chicagoland,IL
Posts: 2,679
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Re: Diagnosis for Whistling noise
Quote:
I like it when things get "PLUGGED"  Pete
__________________
'91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage |
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07-30-2009
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#8 |
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Join Date: Aug 2006
Location: McLean, VA
Posts: 3,723
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Re: Diagnosis for Whistling noise
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Linear Mode
