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chirping noise

Discussion in 'SN95 Cobras' started by Snake Bitten, Aug 20, 2019.

  1. Snake Bitten

    Snake Bitten New Member Established Member

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    Have a chirping noise with my 96 Cobra that goes away when I pul the oil dipstick something i think is going on with the PVC system. Any ideas on most likely causes and fixes ?
     
  2. Tillerman77

    Tillerman77 Active Member Established Member

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    No clue, but since you think it is PCV related, have you replaced the PCV valve?
     
  3. Mojo88

    Mojo88 "Hammer" Time Established Member

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    So, here's my story which I NEVER thought would be relevant to anyone else.

    A few years back I had a supercharged Pontiac Bonneville SSei (3.8L engine). I had to replace the supercharger with a rebuilt one, and whilst doing so I installed new gaskets between the intake and the S/C. Like an idiot, I used a fair (err, lots :oops: ) amount of silicone sealant around all the openings, figuring I'd make sure I only had to do the job once.

    Well, everything seemed fine and then I started noticing these loud chirping noises. I was like ... WTF is that? This continued for a few weeks, the engine ran great and I wasn't too stressed, but I was puzzled. I took it to Pontiac dealer and they clearly heard it but had zero clue as to the cause.

    Then I noticed the noise went away, and I though I was good-to-go, but upon opening hood I notice the dipstick is sticking out a little bit. So I reinstall the dipstick and the chirping starts right away. Then I figured it had to be PCV related as there was a PCV outlet port on the S/C. I took the fitting off and after peering down inside, I could see that my wonderful silicone job had inadvertently plugged the PCV port. I scraped out the port, reinstalled the fitting and the chirping was all gone. :)

    So, my guess (a good one, in this case) is your PCV system is somehow obstructed. I would use 'Occam's Razor' approach and replace the PCV valve first.
     
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  4. ViciousBlack97

    ViciousBlack97 Active Member Established Member

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    I've heard of similar situations where there is extreme crankcase vacuum or pressure that is causing air to be drawn in or expelled through gasket surfaces. Check both of the PCV hoses to make sure there aren't any restrictions
     
  5. Snake Bitten

    Snake Bitten New Member Established Member

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  6. Snake Bitten

    Snake Bitten New Member Established Member

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    I pulled the PVC valve out of the valve cover and the noise stopped so I'm guessing it is not that.
     
  7. Mojo88

    Mojo88 "Hammer" Time Established Member

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    Maybe I'm missing something but if the noise stopped, then that would mean that it IS the PCV valve plugged (or the hose or somewhere along that circuit).
     
  8. triple-s

    triple-s Active Member Established Member

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    What happened snake bitten I thought you we're getting a vette and leaving this forum?
     
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  9. Snake Bitten

    Snake Bitten New Member Established Member

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    I have a Vette that I bought 10 years ago
     
  10. Snake Bitten

    Snake Bitten New Member Established Member

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    I'm going to go with a oil filler Breather cap to relieve the crankcase pressure
     
  11. Mojo88

    Mojo88 "Hammer" Time Established Member

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    Fix it right. Clear up that PCV issue. You'll end up with blow-by going out that cap into engine compartment and maybe getting oil residue all over the engine compartment. Plus the bad oil smell as the vapors settle on the exhaust, it'll smell like burnt oil (likely inside the cabin), no good.

    With engine running, hold your finger over the end of the PCV valve. You should feel a strong vacuum. If not, then figure out what the issue is. As in my example above, it is probably an easy fix.

    Do it right. Don't take shortcuts........ :p
     
  12. Deceptive

    Deceptive Would Smash Premium Member Established Member

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    Didn’t you say you sold the Cobra and were leaving for the trailer park, I mean Corvette forum?




    Sent from my iPhone using svtperformance.com
     
    Last edited: Aug 22, 2019

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