Is it the same as this? >>
Knowledgebase - Infinitihelp.com Forums
"Classification: HA07-001c
Reference: ITB07-007c
Date: March 23, 2009
G35 / G37 / EX35; TAPPING NOISE FROM DASH AREA
WHEN ENGINE IS RUNNING
This bulletin amends ITB07-007b. The Applied Vehicles section has been revised.
No other content has changed. Please discard all previous versions of this bulletin.
APPLIED VEHICLES: 2007 – 2008 G35 Sedan (V36)
2009 G37 Sedan (V36)
2007 G35 Coupe (V35)
2008 - 2009 G37 Coupe (CV36)
2008 EX35 (J50)
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."
Anyhow, the TSB goes on how to clean the debris. Since the engines are the same then the problem most likely also exists with Nissan. Check with the dealer to see if there is a TSB similar to this.