This is a normally a rare occurrence but never the less an important situation to be aware of .This condition is more prevalent when the car has been running on low fuel supply or just been refuelled after an empty fuel tank. Secondly and equally important are DIYer owners are working on their car changing their fuel filters,due to incorrect sealing of the top cap may lead to air entering into the fuel system. The following Honda Vehicles may be affected by this issue. Model Model Code Year Model Civic 5 Door FK3 2012CR-V i-DTEC RE6 2010,2011,2012 The Symptoms Under certain conditions the high pressure fuel pump fitted to Civic / CR-V I-DTEC Diesels may be heard to emit a whistle or vibration noise that can be heard from both the interior and exterior of the vehicle. The Cause Noise occurs because of residual air being caught in the overflow valve on the high pressure fuel pump. (Cross section of overflow valve pictured below) The residual air (A) is bled gradually by fuel flow (C) and returns to the fuel tank via the fuel return line (B). Once the air has bled completely, the noise will disappear. The trigger point for this situation usually follow events when the vehicle has been subject to a low fuel condition or run out of fuel by the customer) or due to a repair process which has introduced air into the fuel system. 12 year model Civic and CR-V Diesels have a slightly different high pressure fuel pump with an improved OHV valve which is able to clear air more efficiently, But this noise may still occur in the above situations. Confirming Issue This noise can be confirmed as coming from the high pressure fuel pump by feel. By touching the rubber fuel return line (A) on the high pressure pump you will also be able to feel high frequency vibrations on this return line as well as hear the noise. These vibrations and noise will disappear once the air, that was trapped within the overflow valve (B) has bled away. There is no fault with the high pressure fuel pump associated with this noise and it should not be replaced for this symptom, just follow the simple repair method below. Repair Method All that is required to clear the noise is to refuel the car (minimum 20 litres) and to take on a short test drive so that the air has had a chance to clear from the high pressure pump.