If your Toyota Highlander is experiencing a whining noise, its is often going to be caused by something in the engine compartment. The likely cause of whining noise will be determined by when you hear the noise, and under what conditions
With that in mind, this page is divided by when you hear the whining noise, and common causes under those conditions.
Before you go any further, is the whining noise constant when you rev the engine? Or does it not change with engine speed? If it changes with the engine, it’s most likely going to be an accessory bolted to the engine (or the radio, shut it off and see if it stops). If it stay constant as you rev the engine it’s going to be something else.
Toyota Highlander Whining Noise When Accelerating
A whining sound when accelerating is almost always caused by a bad accessory attached to your Highlander’s engine. Here are the most common causes of whining noises when accelerating:
1. Bad Alternator
When an alternator is going bad, it’ll often begin to put out a high pitched whining sound. It should also be accompanied by the battery light. If not, it may not be the alternator making your Highlander whine, although it doesn’t rule it out entirely.
2. Power Steering
The power steering pump is a very common reason why your Toyota Highlander might whine when accelerating. If it gets too low on fluid they’ll make the it’ll whine a lot. You need to check the fluid level and fill it back up to the factory fill line.
The pump can also go out. To determine if it is the power steering pump, turn the wheel left and right with the vehicle sitting. Does the sound get louder while turning? That’s a great indication that it is probably the power steering pump making noise. All of your engine accessories will change their wine depending upon the RPM. Only the power steering pump will change with RPM or the steering wheel.
3. Water Pump
When the water pump goes bad, it’ll make a squeaking sound. It’ll often sound like a deeper whine than a bad alternator.
4. Worn Serpentine Belt
Your Highlander’s serpentine belt is responsible for taking the motion from the crankshaft, and using it to turn all of your accessories. When it goes bad, it’ll cause a high pitched whine. This is particularly true when you first start the vehicle. There’s more on this in the whines while starting section directly below.
Toyota Highlander: Whines When Starting
Whining when starting can be frustrating to diagnose, since you constantly have to start and restart the vehicle to duplicate the conditions that caused the sound to begin with.
Here are the most likely causes of a vehicle whining when starting:
1. Serpentine Belt
Your Highlander’s serpentine belt turns all of the engine accessories. As they go bad, they begin to glaze and stretch. When a serpentine belt stretches, it doesn’t grip the accessories that it is turning as well. It’ll squeal until it grabs all the way. They are really affordable.
The radio can accept interference and cause noise when starting the vehicle. This is a great place to start, since it only takes a second. If this does stop the noise, there’s more on this directly below.
The starter may not be fully engaged with the flywheel/flexplate. Or, it could be a situation where it is having a hard time disengaging. If it is even a little bit out of alignment, it’ll be enough to cause a whining noise.
A bad torque converter can cause a whining sound when starting your vehicle. A good place to start would be to check the transmission fluid. You’re going to want to check it for both color, and metal content.
If you see any flecks of metal on there, it is probably going to need serviced. As long as you have the dipstick out, go ahead and check the transmission fluid color. It can tell you a lot about the health of your transmission.
Stereo Making Whining Noise
If your Highlander’s stereo is making a whining noise, it is usually caused by a condition known as “alternator whine”. Alternator whine is a product of a drop in voltage between the radio and the alternator itself. It is usually way more noticeable on the A.M band of the radio. You’ll hear it match the acceleration of the vehicle.
Alternator whine is almost always caused by a corrupted ground wire to the radio. Once a good ground is restored it should go away. Here is a great page with way more info on the subject.
Good luck figuring out what is making your Toyota Highlander make a whining noise. If there is anything that you would like to add, please leave a comment below.