Hearing unfamiliar vehicle noise coming from your car can cause panic in many drivers.
Many do not know enough about vehicle systems to know if it’s something to worry about or not.
You probably know how your vehicle sounds when it’s running properly.
Listening to your car can help you troubleshoot almost any vehicle noise.
Nobody knows your engine better than you do.
So, If it starts to sound odd, or even a little different, there could be a problem.
Consequently, If any unfamiliar vehicle noise suddenly becomes part of your everyday driving experience, it’s time to take action.
Also, Ignoring the symptom won’t make the problem magically go away.
Any delay in repair can provide the time for a problem to worsen and completely fail.
You can often get a good idea of what’s troubling your vehicle by listening to it.
The best way to start diagnosing any vehicle noise is to answer the following questions. If you can answer all of these questions you are 90% there !
- When do you hear the vehicle noise? Is the vehicle moving or stopped?
- What speed does the noise occur at?
- Is it coming from the inside or outside of the vehicle?
- Is the vehicle noise coming from the front, middle, or rear?
- Does engine speed affect the noise?
- Is the vehicle noise a knock or a rattle?
- Does the noise get louder or softer with vehicle speed?
- What is the temperature outside?
- Is the vehicle noise there on a hot day or cold day?
- Is the vehicle noise coming from the engine?
- Does the noise happen while turning or going straight?
- Is the vehicle noise there while accelerating or braking?
So, Armed with these answers you are well on your way to solving your problem.
Common vehicle noise you may hear and their possible causes:
Valve Train Noise
Valve and hydraulic lifter noise has a clicking sound that usually quiets down as you raise the engine RPM’s. A lifter is what opens and closes intake and exhaust valves. Worn or sticking hydraulic lifters can cause these noises. A varnish build up on the lifter surfaces can cause sticking. Low oil pressure can also be a factor. Adding a detergent additive to the oil can sometimes stop this noise. If this doesn’t do away with the noise, then the worn lifters that continue to make noise would require replacement.
Timing Chain Noise
Many of the newer engines have overhead camshafts with longer timing chains. A timing chain connects the crankshaft to the camshaft to insure the valves open at the proper time. Hydraulic tensioners keep the slack tight in these chains. The chains ride against a nylon guide (a chain guide) which, in time, begins to wear.
Consequently, The hydraulic tensioner can not take up the slack, and the timing chain begins to rattle. The timing chains becoming so loose that they whip back and forth against the guides and possibly the timing cover. If the oil pressure is correct, replacement of the hydraulic tensioners and chain guides would be required. A mechanic’s stethoscope is a great tool to pinpoint this noise.
Detonation, Pre-Ignition (Pinging) Noise
You usually hear this noise when accelerating the vehicle. Most people call this a pinging or rattling sound. This noise is caused by an air/fuel mixture in the engine cylinder being ignited prematurely by the heat of compression as the piston is moving up on the compression stroke. If ignition happens before the piston reaches the top of its stroke, this is called pre-ignition or pre-detonation, which can damage the pistons, valves and connecting rods.
They get damaged because the fuel igniting too early produces pressure waves from the fuel’s explosion in the cylinder, which collide with the piston as it’s moving up. And that’s also why you hear the pinging and rattling noises. Some of the causes of this condition are improper fuel octane, engine overheating, improper ignition timing, the EGR valve not functioning properly and problems with the computer or knock sensor.
All these conditions can cause the air fuel mixture in the cylinders to ignite before it’s supposed to. This creates multiple flame fronts in the cylinder fighting each other and causing the pinging and rattling noise. Check your owner’s manual to make sure you’re using the right grade of fuel. Or you can switch to a higher grade for a period and see if the noise goes away. If it doesn’t, you’ll want to look at these other possible causes.
Connecting Rod Noise
Connecting rod noise is caused by excessive clearance between the crankshaft and the connecting rod bearing surface. This happens when you have low oil pressure causing the bearing to run dry of lubrication. The oil gets dirty and grit can wear the surface of the bearings.
The noise is usually heard when you hold the throttle at a steady RPM. If it sounds like a single knock, you (or your mechanic) can isolate the cylinder by disabling the spark or the fuel injector for each cylinder one at a time. When the noise goes away or gets much quieter, you have found the problem. Problems like this require immediate attention because continued running of the engine in this condition will damage the crankshaft and require a major engine overhaul.
Crankshaft Bearing Noise
Crankshaft bearing noise is also caused by low oil pressure which damages the bearing surfaces and could eventually damage the crankshaft itself. This type of noise is usually described as a rumbling or thumping sound deep in the engine when accelerating.
A mechanic will fix the problem by replacing the bearings and solving the oil pressure problem. Bearing shells are what the crankshaft rotates within. If you continue to run the engine with this condition, you will most certainly cause a major engine failure.
Piston Slap Noise
Excessive clearance between the piston skirt and the cylinder wall cause this noise. The usual cause of this problem is cracks in the lower piston skirt. The piston skirt is the lower part of the piston which will develop cracks over time due to metal fatigue. The noise sounds like a muffled bell sound or a hollow clatter deep in the engine and is more noticeable when the engine is cold.
Nothing needs to be done if the noise goes away when the engine warms up. The clearance is reduced by the expansion of the piston skirt as the engine comes up to temperature. In many cases the noise goes away completely.
Piston Pin Noise
Piston pin noise is similar to valve train noise. The noise is unique because you will hear a double knocking sound caused by the lack of oil and excessive clearance between the piston pin and the piston. A piston pin attaches the connecting rod to the piston.
This condition can only be remedied by replacing the piston pin bushings, possibly even the piston itself, along with solving the oil pressure or lubrication problem. Problems like this are usually a result of worn connecting rod and crankshaft bearings which reduces oil pressure.
A whining noise when an engine is running is usually an indication of a bearing that is on the verge of failure. This noise will increase as the engine RPMs increase. There are several items under the hood that can make this kind of whining sound. The water pump, air conditioner clutch bearing, fan belt idler pulleys or belt tensioner, alternator and the power steering pump. These are all possible sources for whining sounds indicating future bearing failure. Whining from the power steering pump will get louder when turning the steering wheel from side to side and the usual cause is low power steering fluid. The best way to diagnose the other bearing noises is with a mechanic’s stethoscope. Failure to repair any one of the items making a whining sound can result in a vehicle break down.
Squeals And Screeching Noise
When you hear squealing or screeching noises coming from your engine this normally signifies you have a problem with one of the drive belts. Either the fan or the auxiliary belt might be slipping, cracked or corroded, but worn pulleys could also be causing the belt to slip. In some instances, the water pump could be to blame, putting extra strain on the belt. If the squealing noise is accompanied by a rise in engine temperature and water loss, the water pump might have failed and needs replacing with a new unit.
Loud Rattling Noise
Rattling from underneath the car could indicate a loose exhaust bracket or a heat shield that has worked itself loose and needs repairing or replacing. When the rattling occurs under the hood, this is more serious and needs immediate attention straight away. There are a number of causes for engine rattles, including problems with the idler pulley, air conditioning compressor clutch, or the belt tensioner.
More seriously, if the engine starts to rattle and the oil warning light comes on while you are driving, pull over as soon as you can safely do so, and shut the engine off.
Continuing to drive the vehicle with the rattle and oil light on and there’s every chance you might cause catastrophic damage, and need a replacement engine.
Never ignore any warning signs as they will always get worse.
Vehicle Noise Conclusion
Vehicle Noise is just part of operating a vehicle. Tire treads hum against the asphalt, wind whistles as it passes around outboard mirrors, plastic bits and pieces in the dashboard generate little squeaks as they rub together and so forth. If it starts to sound odd, or even a little different, there could be a problem. If any unfamiliar vehicle noise suddenly becomes part of your everyday driving experience, it’s time to take action.
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