Whining Noise From the Engine? What Rises and Falls With What

A whining noise is one of the more frustrating things to describe, because it is not dramatic and it does not obviously belong to anything. It just sits there, present, getting slightly worse.

A whining noise from the engine narrows down quickly with one question: what does it track? Engine speed, road speed or steering input. Those three lead in completely different directions, and you can establish which in a single short drive.

The test that separates them

Somewhere safe and quiet, with the radio off and a window down.

1. Get to the speed where you hear it clearly.
2. Select neutral and let the car coast for a moment. If the whine continues unchanged, it tracks road speed. If it drops with the revs, it tracks engine speed.
3. Stationary, with the engine running, rev gently. A whine that rises with revs while parked tracks engine speed.
4. Stationary, turn the steering slowly lock to lock. A whine that appears or worsens is the power steering.
5. Note whether it changes when you switch the air conditioning on, which loads one of the belt-driven components.

Those four minutes usually do more than any amount of describing the noise afterwards, and they give whoever looks at the car a real starting point.

If it tracks engine speed

You are looking at something driven by the auxiliary belt at the front of the engine, or at the belt itself.

• The belt tensioner or an idler pulley, whose bearings wear and whine. Common and usually inexpensive.
• The alternator bearing, often with a warning light eventually.
• The water pump, if driven by the auxiliary belt, which may come with a coolant leak.
• The air conditioning compressor, which is the one that changes when you switch the air conditioning on.
• The belt itself, glazed or worn, which typically squeals more than it whines but can do both.

These are worth attending to rather than living with. A pulley bearing that seizes can throw the belt, and on many engines the auxiliary belt drives the water pump and the alternator, so losing it strands you quickly.

If it tracks road speed

Then it is rotating with the wheels or the transmission, and the engine has nothing to do with it.

A wheel bearing is the most common cause, and it usually presents as more of a hum or a drone that changes when you sweep gently left and right at speed, because cornering loads one side more than the other. Tyres also produce road-speed noise, particularly when worn unevenly, and are worth ruling out before anything is replaced.

A whine that varies with which gear you are in, rather than purely with speed, points at the gearbox or differential instead. That is a different conversation and the fluid history matters.

If it appears when you steer

On a car with hydraulic power steering, a whine that rises when you turn, and is worst at full lock, is the power steering pump.

The first thing to check is the fluid level, because a low level causes exactly this noise and it is a two-minute check. If it is low, something is leaking, and topping up without finding it is a temporary measure rather than a fix. Look for wetness around the pump, the hoses and the rack.

Holding the steering at full lock for more than a moment is worth avoiding regardless. It puts the pump against its relief valve and is a genuine cause of premature wear, quite apart from the noise it makes.

Many newer cars have electric power steering with no pump and no fluid at all, in which case this whole category does not apply and the noise is something else.

The electric car version

Worth a note because it causes unnecessary worry. Electric cars whine by design: the motor and reduction gear produce a rising tone with speed, and some cars add an external sound generator at low speed deliberately.

That is normal. What is not normal is a change: a new tone, a whine that has become noticeably louder, or one that appears only under load or only when regenerating. The baseline is whatever your car has always done, and it is the deviation that means something.

How urgent is it?

What to record before you book it in

A whining noise is one of the hardest faults to reproduce on demand, and a workshop that cannot hear it cannot diagnose it. A few notes make an enormous difference to whether it is found first time.

• Whether it tracks engine speed, road speed or steering, from the coasting test above.
• The speed or rev range where it is loudest, and whether it disappears above or below that.
• Whether it is worse cold, worse warm, or the same throughout.
• Whether it changes with the air conditioning on, in a turn, or under load going uphill.
• When it started, and whether anything happened around then such as a service, a wheel change or a pothole.

A short recording on a phone with the window down is genuinely useful too. It is imperfect, but it captures the character of the noise better than any adjective, and it settles the question of whether the person driving it can hear what you hear.

Most causes of a whining noise are wear rather than emergency, with two exceptions worth knowing.

Anything belt-related deserves reasonably prompt attention, because losing the belt takes the charging and often the cooling with it. A wheel bearing that has gone from a faint hum to an obvious drone is also worth acting on rather than monitoring, since the failure mode at the end is not graceful.

The rest can usually wait for a convenient appointment. What is not useful is turning the radio up, because a whine that is ignored for six months rarely costs the same as one investigated in a fortnight.