Some 2007-2008 Nissan 350Z, 2009 350Z roadster and 2009 370Z coupes may exhibit a tapping noise coming from the dash area when the engine is running at operating temperature. The noise may sound like a screwdriver being tapped on the workbench. The tapping speed increases and decreases with engine rpm and may require engine rpm of about 3,000 for the noise to be heard.
The noise is coming from inside the heater core, requiring a back flush to remove gray silicone debris.
- Confirm that the noise is coming from the heater core as follows:
- Confirm that the engine is at operating temperature.
- Turn the engine OFF.
- Use blunt pinch clamps to pinch the heater core inlet and outlet hoses (this will stop water flow through the heater core).
- Start the engine and check for the noise, gradually increasing engine speed to 3,500 rpm. DO NOT run the engine for more than five minutes with the heater hoses pinched.
- If the noise is gone, this bulletin applies. Go to Step 2. If the noise remains, this bulletin does not apply. Refer to ASIST and the service manual.
- Back-flush the heater core as follows:
- Follow service manual procedures (section CO) to drain the cooling system.
- Disconnect the heater core inlet and outlet hoses.
- Connect a garden hose to the heater core outlet. NOTE: Use a water supply with “full building site” water pressure. In most shops, the shop water hose that pulls down from the ceiling does not have enough water pressure for this procedure.
- Connect a hose from the heater core inlet side into a clean bucket (minimum five gallon bucket recommended).
- Turn on the water supply.
- Let the water flow through the heater core until the bucket is full.
- Inspect the bucket, looking for silicone debris (long piece or balled-up piece of gray silicone). If you find the silicone, the back-flush is complete. If not, repeat the back-flush until you find the silicone in the bucket.
- Reconnect the heater core hoses and refill the cooling system.
- Run the engine at operating temperature to confirm that the tapping noise is gone.