What’s that noise coming from my car?

[Nate4x4]

Whether it's a worn belt or a squeaky power steering pump, we'll help you figure out that pesky noise under the hood

 

 

Noises have to be one of the biggest peeves owners have about their vehicles. If it’s one that isn’t easily identifiable, that can drive the frustration level right round the bend. Engine pulley and belt noises need to be heeded (like many other automotive cacophonies) to avoid a breakdown or a more expensive repair bill.

When a whining noise starts under the hood, most drivers automatically assume a new belt is needed. That might be correct, but not always: Eliminating the belt as a cause is as easy as squirting it with a shot of silicone spray, or even water. If the noise temporarily goes away when the belt is treated, that’s most likely the problem.

Another helpful do-it-yourself diagnosis is to check the power steering fluid level. If it’s low and the whining noise changes noticeably when the steering is moved back and forth, the pump may be running low. Leave a power steering pump low on fluid and you can end up ruining the pump and risk damaging the steering gear itself. These systems don’t have too much fluid volume, so being even as little as half a litre low can cause problems.

If a treated belt and/or steering shuffle don’t bring any noticeable changes to the whining sound, you may be dealing with a noisy alternator. Unless you have a battery/charging system tester, it’s hard to apply a load to these systems to see if the noise changes.

But if you’ve got a good ear, try turning on heavy electrical demand accessories and units to increase the alternator’s load. Turn on the headlamps, rear defroster and seat heaters (if equipped) at the same time while listening to the running engine.  If the noise changes, you may have an alternator bearing on the way out.

Air conditioning compressors can also be a source of engine whining noise. They can easily be activated and deactivated (even in cold weather) by selecting the ‘max A/C’ setting. The problem with diagnosing a bearing or pulley noise from an A/C compressor is that even when they’re not running, they have a pulley that continues to turn. It has its own bearings in addition to the bearings internal to the compressor.

Water pumps can also create bearing noises and usually, by the time their bearings are gone far enough to hear, they usually develop a noticeable amount of play. So with the engine off, locate the water pump pulley and try to move it.  If you can easily move the pulley any more than a fraction of an inch, the pump is likely in need of replacement.

Don’t forget: Electric cooling fans as a source of unwanted noise.  This would be especially apparent if the noise only occurs during stop-and-go driving, when the fans are likely to be activated by higher coolant temperatures. Shops can use special diagnosis equipment to activate cooling fans for testing. A skilled technician can achieve the same effect by disconnecting the fan motor(s) to apply direct battery voltage to its terminals.