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chirping on decel
hi everyone,
need help identifying a mystery sound... 80SC - i get a chirping sound when letting off the throttle (chirp, chirp, chirp... chirp). i thought it was my 3 broken head studs but i just had them all replaced (like a big storm cloud lifted from my shoulders). if it's bad alternator bearings the noise would be constant correct? only happens when i let off the throttle, doesn't matter what temp the engine is, does not happen at idle. any advice on what to rule out and what to start investigating is appreciated ap |
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Member 911 Anonymous
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When I read "chriping" I think of the tires spinning.. Is this what you mean?
At what RPMs do you hear the chirps?
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'85 Carrera Targa Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace PCA/POC |
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Registered
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it's definitely not tires. it does not occur when i accelerate, only when i let off throttle at any rpm until get to idle revs and it stops. like a little bird or rodent under my hood, or air/exhaust pressure being released through a small space.
i ripped out all the carpet and sound insulation so i can clearly hear it from the cabin, maybe i'll post a sound clip tonight. |
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Registered
Join Date: Apr 2009
Location: Central Canada
Posts: 1,089
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This happens when slowing down in gear?
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RETIRED
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Could be the decel valve.....block it off and try again.
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1983/3.6, backdate to long hood 2012 ML350 3.0 Turbo Diesel |
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Flat Six
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Also check belt/belt tension. Had a similar issue w/worn (slightly glazed) belt -- differential speeds between crank and fan pulleys led to small squeal on deceleration.
HTH
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Dale 1985 Carrera 3.2 -- SOLD 2026 Jaguar F-Pace / 2025 Ford Bronco Sport |
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Registered
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Are you running A/C? My A/C belt does this when A/C is on.
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'80 RoW 911 SC non-sunroof coupe in Guards Red It's not a Carrera.... It's a Super Carrera! |
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Registered
Join Date: May 2005
Location: Cridersville, OH
Posts: 1,879
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Loosen the oil cap and see if it still does it. I had to replace my restrictor in the breather hose, seems the vacuum from closed throttle would make the seal on the cap "chirp".
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75 911 Indian Red- RUFWAN2B 2000 Boxster 2000 & 2007 Dobies www.stahlwerks.com Cages and preparation for your Porsche “People who never make mistakes must get tired of doing nothing” Bill : The origin of the orgy of Porsche |
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RETIRED
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Never heard of the problem but the suggestion sounds plausible.......
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1983/3.6, backdate to long hood 2012 ML350 3.0 Turbo Diesel |
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Flat Six
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Hey Andrew -- any update/resolution?
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Dale 1985 Carrera 3.2 -- SOLD 2026 Jaguar F-Pace / 2025 Ford Bronco Sport |
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Registered
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hi guys, sorry i was out of town til now...
andyt: yes only happens when slowing down in gear or between shifts, if i engage the clutch or put into neutral... nothing. Joe Bob: do you mean by blocking off the connection at the back of the air boot? what would be your suggestion? Flat Six: i replaced the belt about 4 months ago, tension seems ok. Josh D: my AC hasn't worked in years so i've basically pulled out everything i come across AC related... i think. DUK: interesting, i will try this. here is a one minute video clip, chirps start at the 19 second mark: ap |
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RETIRED
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The suggestion was to replace or clean the restrictor valve....
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1983/3.6, backdate to long hood 2012 ML350 3.0 Turbo Diesel |
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Registered
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Any resolution to this? My 80 SC engine makes a chirping sound on decel, sounds like a wastegate popping off.
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Rob 76 widebody project 86 Carrera Coupe 01 BMW X5 98 Jaguar XJ8 |
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86FlatSix
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Do you hear it more or less at the front? I have the same thing going. I hear chirping a the dash area but its intermittent and not a common noise. Sometimes its there sometimes its not. I was thinking it could be from the AC blower or something.
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74 BMW 2002 (rust rocket) 86 911 Coupe (weekend warrior) 09 997.2 C2 (semi-daily) |
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This sounds like it'from the back. I found the gasket on my oil cap split. I am making a new one, will post how it works.
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Rob 76 widebody project 86 Carrera Coupe 01 BMW X5 98 Jaguar XJ8 |
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Registered
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No difference. It's not a consistent sound, so it's hard to troubleshoot.
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Rob 76 widebody project 86 Carrera Coupe 01 BMW X5 98 Jaguar XJ8 |
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Registered
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Does this model have an ambient air valve? If it does, I'd check it.....
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Neil 1987 Carrera, Grand Prix White, 2009 Carrera C4S, Meteor Grey Metallic (X) [B] 2011 BMW X5[B] 'Success is not final, failure is not fatal. It is the courage to continue that counts' |
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Slow old car
Join Date: Jan 2014
Location: SE PDX
Posts: 442
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My car makes this same noise, as heard in the video, on deceleration in gear. I just went for a drive and on long downhills in gear it was happening quite a bit.
Any tips from anyone whose been able to resolve this? I hate to bump ancient threads like this but this is the first one I’ve found with the exact symptom and a video, and there isn’t a resolution!
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Mike 1980 911 SC 3.1 Coupe // 1986 VW Vanagon Syncro EJ22 // 2015 Macan Turbo // 2017 i3 REX |
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Hi Mike, first of all congratulations on your new car.
I still have the sound and yes I know how old this thread is LOL! I don't think it's the head studs from all the posts I've read when you Google "what does a broken 911 head stud sound like", it really sounds more like an air/exhaust pressure type of thing, rather than a piece of metal slamming around type thing. I drive my car all the time, it run great and hasn't gotten worse. My mechanic says it's running great so just leave it but I'm going to a new shop for my next tune up and I can post what they say. Last edited by andrew1980911SC; 06-30-2019 at 03:24 PM.. |
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Crotchety Old Bastard
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I believe I know the sound you are talking about. I've heard it a couple of times, both from cars that sat a lot. The chirping sound comes from the transaxle area and sounds like a metal on metal "cheap". On both cars that I had experience with the chirp was very reproducible and happened during acceleration instead of decal but it may be the same culprit. The noise was caused by movement in the drive train putting the transaxle in a bind with the mounts on one car and the clutch omega spring hitting the heat exchanger on the other. Same noise on both. Look for worn mounts and see if you can spot moving parts getting too close to one another. May be able to see movement by having someone rev the engine while on a lift.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds '78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8 |
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