logan1080

2006 z06 with 16,000 miles. I bought the case car with 4,000 miles and it's always made this noise under firm acceleration. It sounds like a piece of plastic knocking against the windshield or something just under the hood. It only happens in the middle of the rpm range, around 4000 rpm, and goes away under hard acceleration. Is this normal? I can't find anything loose.

12leavu

Good luck.


https://www.corvetteforum.com/forums/c6-z06-discussion/3687334-another-strange-noise-thread-searched-a-lot.html

My phone is not allowing me to make this a clickable link, but there's some useful info in that thread, but if it's doing what mines doing, good luck finding out, and let me know when you do.

dmuellenberg

Some people have reported that the cowl in front of the windshield has come loose and will make a vibrating noise at high speeds.

z06clif

I remember something mentioned like this.

Clif

Bill Dearborn

There is a TSB about a noise that can be heard coming from the engine compartment and may sound like it is coming from the base of the windshield.

#08-06-01-019: Rattle/Tappign Type Noise Heard Under Hood (Diagnose and Replace Engine Oil Tank Transfer Tube Seal (O-Ring)) - (Aug 13, 2008)


Subject: Rattle/Tapping Type Noise Heard Under Hood (Diagnose and Replace Engine Oil Tank Transfer Tube Seal (O-Ring))


Models: 2006-2009 Chevrolet Corvette Z06

2009 Chevrolet Corvette ZR1

with 6.2L or 7.0L Engine (VINs R, E -- RPOs LS9, LS7)




--------------------------------------------------------------------------------

Condition
Some customers may comment on a rattle or tapping type noise that is heard under the hood at just above idle, usually 1200 to 2200 RPM. In some cases, this noise may also be heard on the inside of the vehicle and be more pronounced on the passenger side.

Cause
This noise may be caused by the internal transfer tube in the engine oil tank hitting the inside of the tank cover. The seal (o-ring) that secures the tube in place may split and slide down the tube allowing the tube to be loose.

Correction
Diagnose the noise by raising the vehicle on a hoist and holding the throttle at about 1500 RPM to duplicate the condition. Use a stethoscope or chassis ears and place them on the side of the engine oil tank. If the noise is detected, perform the procedure outlined below. If the noise is not detected, continue following published diagnostics in SI.

Remove the engine oil tank from the vehicle. Refer to the Oil Tank Replacement procedure in SI.
Remove the eight bolts that secure the tank top.
Separate the tank. Check the seal (o-ring) for proper position and damage. Replace the seal (o-ring) if damaged with P/N 24576940.
Reinstall the tank top and secure with the eight bolts.
Install the engine oil tank into the vehicle. Refer to the Oil Tank Replacement procedure in SI.
Parts Information
Part Number
Description
Qty

24576940
Seal (O-Ring), Engine Oil (Tank Transfer Tube)
1


Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J7537*
Diagnose and Replace Engine Oil Tank Transfer Tube Seal
1.5 hrs

*This is a unique labor operation for bulletin use only. It will not be published in the Labor Time Guide.




GM bulletins are intended for use by professional technicians, NOT a ""do-it-yourselfer"". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

This is almost a $400 repair at a dealership. GMPP computer system told the dealer they didn't cover it due to it being an O Ring but when I called and explained it was inside the engine oil tank and had the potential to cause damage to the engine they decided to cover it.

Bill

dmuellenberg

That bulletin states that the noise is heard just above idle - around 1200 to 2200 rpm. The OP claims his noise is around 4000 rpm under moderate acceleration, so I don't this would be his problem (but you never know).

0Anthony @ LGMotorsports

Always RPM related or does it do it with speed as well?

Matter which gear it is in?

Bill Dearborn

The problem in the bulletin can definitely be heard when the engine is idling and you place a stethoscope or a wooden dowel rod against the oil tank and listen to the internal sounds of the tank. When mine went it made the noise through a fairly large rpm range but when I put a dowel rod between my ear and the oil tank the noise of the tube was very loud and I knew I had located the problem. Maybe it can be heard at higher rpms at first but gets louder and more noticeable at lower rpms as time goes by. Opening the hood while the engine is idling and using a couple of foot long piece of dowel to listen to the tank can quickly eliminate or confirm whether the noise is coming from there. Better than sitting around and scratching your head.

Bill