The Car Whisperer: How to Identify the Cause of Engine Noises

By July 16, 2014Engine, Fuel
How to Identify and Diagnose Engine Noises

Growing up, there was always that one guy down the street who was admired by all the local gearheads – a car whisperer, who could immediately tell you about every bearing, bushing, belt, and part that was wrong with your car just by listening to it.

Engines are extremely vocal when it comes to communicating their mood and make a variety of distinct noises to tell you when something is wrong. By learning their language you’ll be able to pinpoint the problem and intervene before a simple repair turns into a major catastrophe. Some can be tricky to decipher, but most of them can be decoded right in your driveway, if you know what you’re listening for and how to listen. So, grab a 3-foot length of heater hose and fuel line, pop the hood, and let’s take a listen.

The Belt Squeal

This is probably the easiest engine noise to decipher. You probably hear it several times a day, in fact (hopefully from other cars on the road). It’s a squealing sound that starts when you step on the accelerator and usually goes away after five to ten seconds. At first, it’s nothing more than embarrassing and annoying. However, if left to fester, it could end up leading to much bigger problems.

The squeal is coming from the accessory drive belt(s). It/they have either become stretched or worn out and need either re-tensioning or replacement. With a serpentine belt, it could also mean that the belt tensioner (spring-loaded pulley that pushes against the belt providing tension) has become worn out.

This isn’t an emergency if it’s just started to make itself heard. But you should take a look at it and correct the problem when you have a chance. Fixing this early is much less expensive then having to deal with engine damage down the road. Grab the belt and twist it 90 degrees. Look at the side that contacts the pulleys. Is it shiny or cracked? If so, replace it. If not, re-tension it. Or, replace the tensioner.

The Snake Under the Hood

You have your car idling somewhere, maybe letting the AC cool the interior down before getting in and you hear something that sounds like snake under your hood – hisssssssssssss. If you live out in the country, it might be a snake. Chances are, it’s not, though.

Keep the engine running and find the heater and radiator hoses. Squeeze them. Do they feel soft or look/feel wet? You’ve got a pinhole leak. If they feel and look fine, follow them to where they connect to the engine, radiator, and heater core. Look for steam or a fine jet of liquid coming out. If you see something escaping, tighten the clamp.

If none of these look-sees turns anything up, it’s time to start looking at vacuum lines. A can of spray carburetor and choke cleaner will help. There’s a 3/8-inch vacuum line going to the brake booster. Listen to it at the booster and where it connects to the engine. Does the sound change? Next, spray the cleaner over the vacuum lines. On newer cars, these are mostly color-coded plastic lines. Also, spray the joint between the intake manifold and the head(s). Be careful not to spray carb cleaner next to spark plugs or their wires. If the engine races or stumbles, you’ve found a vacuum leak.

The Tick Tick Tick

If you’re hearing a somewhat higher-pitched ticking sound coming from the upper part of the engine, you’re probably hearing an exhaust leak. There are valves that allow the fuel and air mixture into the engine while letting the exhaust out which are operated by hydraulic lifters. These lifters require a certain oil pressure to operate properly so be sure your oil level isn’t low.

Take that length of hose I mentioned above, hold one end to your ear, and carefully and slowly move the other end around the connection between the head and the exhaust manifold. If the ticking is slightly lower in pitch, you’re probably hearing either a flat cam lobe, or a soft lifter. This is a more extensive repair but can be done in a few hours with the right Chilton’s or Haynes motor manual.

The Even Worse Knock Knock Knock

No, this doesn’t mean that someone wants in. It’s bad. It means that one or more of the bearings on your crankshaft have failed and probably signifies worse damage is happening. Take your hose and hold it near the oil pan. The knocking should get louder the closer you get to the pan. If you’ve got time and energy, you can fix this, with the right tools and equipment – and a motor manual. Your engine will have to be removed and the bottom end of the engine will need to be disassembled and rebuilt.

This is by no means an all-inclusive list of the different noises you can hear coming from your engine. But, by being able to identify the most common noises you’re well on your way to being the neighborhood car whisperer.

Photo credit: mr.bologna

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