How to Repair a Whistling Noise

When a car starts to produce a whistling sound it can be very loud or hardly audible. In either case a whistling noise is not normal at anytime. Some whistling noises are quite simple to fix while others are a little more difficult to find. Whistling noises can be aligned with the engine speed while other whistling noises are created and change with the speed of the car. In all cases the whistling can only be produced by small hole when air is passed through it. The pitch of the whistle depends on the rate in which the air is traveling through the hole. Fortunately there are a limited number of causes that would create this whistling noise. We have list common; engine running with car not moving and car in motion problems below:

Engine Running, Car Not Moving - This section includes symptoms that present themselves when the engine is running only.

Checking for a Vacuum Leak - Your car's engine relies on a constant amount of vacuum to operate properly. Engine vacuum is held by a series of gaskets and hoses. If one of these vacuums lines or gaskets develop a leak it can cause a whistling noise that is audible. This whistling noise will change as the engine throttle is moved. Check for broken or dilapidated vacuum hoses on and around the engine. Vacuum hoses are typically connected to the engine intake manifold and will supply engine vacuum to various accessories like power brakes. Some cars are designed with a larger vacuum transfer hose like Ford that connects the intake manifold to the IAC (idle air control) motor. A broken or dilapidated vacuum line or air intake boot can cause the engine to lose vacuum which will allow the engine to run rough and stall. Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. Also have a helper rest their foot on the gas pedal just enough to keep the engine running if it is stalling. Check the engine when it is running to listen for any whistling noise coming from the engine that is not usually present. Follow the noise and inspect vacuum lines in that area. Also, when the engine is running it will pull inward a broken or weak piece of the hose to create a larger vacuum leak. Check the integrity of all vacuum hoses at each end of the hose. Typically this is where a vacuum hose fails.

Failed Air Intake Boot
Failed Air Intake Boot

How to Replace an Air Intake

Check Alternator, Battery and Charging System - A battery is needed to power the operating system of your car. Once the vehicle is running an alternator that is driven by the engine charges the battery. While in operation the alternator creates electricity, about 13.6 to 14.3 volts, and recharges the battery to its original state of charge. The alternator is one of the hardest working electrical components in your vehicle. When your vehicle is running the alternator is busy creating electricity to provide the engine and the car accessories with needed power. If high resistance exists between the alternator and battery it can cause the alternator to overwork. When the alternator is overworking it can produce a whistling noise that can vary with engine speed. To check for this condition inspect all electrical wires at the battery and alternator for corrosion. Replace all corroded wiring and recheck system.

Battery Terminal Corrosion

Car Moving: This section includes symptoms that present themselves when the car is in motion

Checking Window Seals - The window seals (weather stripping) in your car are used to seal the water and wind for entering the passenger compartment. When these seals fail from damage or are eroded by the weather they can allow wind noise to enter the passenger compartment. This failure can cause a whistling noise as the car is driven. Some noises are only present when the vehicle is driven at certain speeds such as 55 MPH. These whistling noises can be difficult to find since you are driving at the time. Have a passenger help with the diagnosis by running their hand along the area the noise is being generated from. Once the noise source has been located replace or repair the failed seal and recheck.

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Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-08-16)