“I hear a noise!” That’s a customer complaint that might
encourage you to suddenly take a long lunch. But before you run
off for a BLT, check a TSB! Conditions, such as random noises,
are often already known by the manufacturer, and a solution may
be available. TSBs (technical service bulletins) are just a few
clicks away when you subscribe to OEM repair information.
In this particular case, your customer is driving a Nissan® and
reports a tapping noise coming from the dash area when the engine
is running at operating temperature. This particular noise sounds
like a screwdriver being tapped on the work bench. The tapping
speed increases and decreases with the engine RPM and may require
an RPM of about 3000 for the noise to be heard. Step one is to
determine if the noise is coming from inside the heater core. If
so, proceed to the service procedure to correct the condition.
2007-2008 G35® Sedan
2009 G37® Sedan
2007 G35 Coupe
2008-2009 G37 Coupe
ACTION: “Back-Flush” the heater core to remove
gray silicone debris.
IMPORTANT: The purpose of ACTION 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.
Review safety procedures in ALLDATA Repair® before beginning.
Confirm the noise is coming from the heater core as
Confirm 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 the water flow through the
Start the engine and check for the noise; gradually
increase engine RPM to 3500.
NOTE: 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
If the noise is still there, this bulletin does not
apply; refer to OEM procedures for further diagnostic and
“Back-Flush” the heater core as follows:
Follow OEM procedures to drain the cooling system.
Disconnect the heater core inlet and outlet hoses
Connect a water hose (garden hose) to the heater core
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 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.
Turn ON the water supply.
Let the water flow (back-flush) through the heater core
until the bucket is full.
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.
Reconnect the heater core hoses and refill the cooling
Refer to OEM procedures for cooling system refill
Run the engine at operating temperature to confirm the noise
NOTE: Follow OE information or standard
practices for all procedures and sub-procedures.
NOTE: This Repair/Service Procedure is
intended for use by trained, professional technicians with
the knowledge, tools and equipment to do the job properly and
safely. It is recommended that this procedure not be
performed by “do-it-yourselfers.”
Edited by ALLDATA’s staff of automotive repair experts.