A/C - Tapping Noise From Dash With Warm Engine
Classification: HA08-002BReference: NTB08-053B
Date: March 23, 2009
350Z-370Z; TAPPING NOISE FROM DASH AREA WHEN ENGINE IS RUNNING
This bulletin amends NTB08-053a. The Applied Vehicles section has been revised. No other changes have been made. Please discard the previous version of this bulletin.
APPLIED VEHICLES:
2007 - 2008 350Z (Z33)
2009 350Z roadster (Z33)
2009 370Z coupe (Z34)
IF YOU CONFIRM
A tapping noise coming from the dash area when the engine is running at operating temperature,
NOTE:
This tapping noise, if it should occur, sounds like a screwdriver being tapped on the work bench. The tapping speed increases and decrease with the engine RPM and may require engine RPM of about 3000 for the noise to be heard.
DETERMINE IF
The noise is coming from inside the heater core (see Service Procedure).
ACTION
"Back-Flush" the heater core to remove gray silicone debris.
IMPORTANT:
The purpose of "ACTIONS" (above) is to give you a quick idea of the work you will be performing. You MUST closely follow the entire Service Procedure as it contains information that is essential to successfully completing the repair.
CLAIMS INFORMATION
SERVICE PROCEDURE
1. Confirm the noise is coming from the heater core as follows:
a. Confirm the engine is at operating temperature.
b. Turn the engine OFF.
c. Use blunt pinch clamps to pinch the heater core inlet and outlet hoses; this will stop the water flow through the heater core.
d. Start the engine and check for the noise; gradually increase engine RPM to 3500.
NOTE:
Do not run the engine for more the 5 minutes with the heater hoses pinched.
^ If the noise is gone, this bulletin applies, go to step 2, below.
^ If the noise is still there, this bulletin does not apply; return to ASIST and the Service Manual for further diagnostic and repair information.
2. "Back-Flush" the heater core as follows:
a. Follow Service Manual procedures (section CO) to drain the cooling system.
b. Disconnect the heater core inlet and outlet hoses.
c. Connect a water hose (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.
d. Connect a hose from the heater core inlet side into a clean bucket (minimum 5 gallon bucket recommended).
NOTE:
You must capture the water coming out of the heater core so you can confirm the silicone debris came out during the back-flush.
e. Turn ON the water supply.
f. Let the water flow (back-flush) thought the heater core until the bucket is full.
3. Look in the bucket to find the silicone debris (long piece or balled-up piece of gray silicone).
^ If you find the silicone, back-flush is finished.
^ If you don't find the silicone, repeat step 2 (back-flush) until you find silicone debris in the collection bucket.
4. Reconnect the heater core hoses and refill the cooling system.
^ Refer to the Service Manual section CO for cooling system refill procedures.
5. Run the engine at operating temperature to confirm the noise is gone.