Engine Rattling Noise – Where Is It Coming From – How Bad Is It

Engine Rattling Noise - Where Is It Coming From - How Bad Is It
Engine Rattling Noise - Where Is It Coming From - How Bad Is It

So, you start your engine like normal but, you hear a engine rattling noise, you’ve never heard before.

Consequently, an engine rattling noise in your engine, can spring up, from a number of different sources.

So, The first part of diagnosing an engine rattling noise, is always to determine, where it is coming from.

Then establish when the noise occurs, and how your engine behaves when the noise starts.

It can be a little nerve-racking, as some sounds can be indicators of serious problems, while others have simple fixes.

Engine Rattling Noise - Where Is It Coming From - How Bad Is It
Engine Rattling Noise – Where Is It Coming From – How Bad Is It

Responding appropriately to the sounds your engine makes, can prevent problems from worsening, thus saving you time and money.

So, whether it’s an engine rattling noise when accelerating; or some kind of spark knock or just a general engine noise; there’s one thing that’s true of them all, it’s never a good idea to just leave it alone.

A quiet engine makes for a happy driver, but once a rattle or some other odd noise emerges; your peace of mind may evaporate. Consequently, you have a great many moving parts inside your engine. As they wear, you may hear rattling noises from a variety of sources:

Common Reasons For Noise:

Oil And Fuel-Related Noises:

Let’s start with rattling noises under the hood, that are caused by oil or fuel-related problems:

Reason, Low Engine Oil Level:

So, Your engines oil pump circulates engine oil through the engine, lubricating the internal moving parts. Over time, the engine can consume, burn or leak oil. If the oil level gets too low, you can have a situation, where the oil pump sucks air into it; and the air gets pumped through the engine along with whatever oil is remaining. As a result, This can cause a rattling or ticking noise from within the engine.

Low Engine Oil Level
Low Engine Oil Level

Solution:

Shut off the engine immediately. Use the oil dipstick to check the engine oil level. Pull out the dipstick, wipe it off with a paper towel, then reinsert and check the level. It should be between the two marks on the dipstick. If the level on the dipstick is low or nonexistent; add the specified oil for your vehicle, until it is up to the full or maximum level. If you have a major oil leak or are burning a lot of oil; the cause should be found and corrected. Otherwise, you’re likely headed for an engine failure.


Reason, Pinging From Low-Octane Fuel:

So, Your engine needs fuel with the correct octane rating to operate properly. If you hear a pinging or rattling sound when accelerating, low-octane fuel could be the cause. Pinging (also called pre-ignition or detonation) can also be the result of carbon deposits; a bad knock sensor, overheating or incorrect ignition timing.

Engine Rattling Noise
Pinging From Low-Octane Fuel

Solution:

Fill your fuel tank with premium fuel and see if the problem goes away. If not, you will have to track down the exact cause. Get this fixed immediately, because it can damage or destroy your engine.


Noises From Internal Engine Parts:

There are many moving parts within your engine that can cause a rattling noises:

Reason, Timing Chain Or Belt Noise:

Your engine’s timing chain or belt connects the crankshaft to the camshaft; for proper operation of the valve train as described above. Modern overhead cam engines have very long chains and belts, which use hydraulic tensioners to keep the chain taut. But, Over time, the nylon chain guides wear, and the tensioners can’t manage the slack in the chain or belt. You hear a rattling noise made by the chain or belt whipping around, untensioned, inside the timing chain cover. Consequently, This noise rises and falls with the engine (RPM)s.

Engine Rattling Noise
Timing Chain Or Belt Noise

Solution:

Replacement of the hydraulic tensioners and the chain guides may be necessary. If you have a timing belt, check it for wear and replace it; if you are near the prescribed replacement interval.


Reason, Valve Train Noise:

The valve train is the system in your engine that’s driven by the camshaft; that opens and closes your engine’s valves. The valve train allows fuel into the cylinders and lets the exhaust gases out. Consequently, The valve lifters are the components that do the actual opening and closing of the valves. They can be either mechanical or hydraulic. If they get worn, stuck or out of alignment, a rattling noise may be heard, especially at low (RPM)s.

Engine Rattling Noise
Valve Train Noise

Solution:

Depending on the type of lifter and the exact cause, the fix may involve adjusting the valves. Also, using a detergent additive, if the lifters are coated with varnish and sticking; or replacing the lifter if it is defective.


Reason, Piston Slapping Noise:

If you have a high-mileage vehicle with a worn engine, the pistons may fit in the cylinders very loosely. During a cold start, this may show up as a rattling noise. It typically goes away once the pistons expand from the heat of the engine.

Piston Slapping Noise
Piston Slapping Noise

Solution:

Fitting oversize pistons will solve the problem, but this is a very expensive fix. It may not be worth doing on a high-mileage vehicle, that has lost most of its value. If you can live with the noise, it is unlikely to cause any further issues.


Reason, Connecting Rod Knocking Noise:

Your connecting rods are the parts that transmit the rotary motion of the crankshaft; to the up-and-down motion of the pistons. Rod knocking noises are the result of wear from insufficient or dirty oil; and can wear down the surfaces of the bearings. As a result, This causes excessive clearances between the bearings and the crankshaft.

Connecting Rod Knocking Noise
Connecting Rod Knocking Noise

Solution:

Once you hear the noise, you will need major engine work, which will be very expensive. If not fixed, some or all of these rotating parts, can fail and destroy the engine.


Rattling Noises From Other Parts, Attached To The Engine May Include:

  • Drive belt issues
  • Bad water pump
  • Broken harmonic balancer
  • Defective starter
  • Bad fan clutch
  • Failing idler pulley
  • A cracked flex plate
  • Loose heat shielding
  • Loose torque converter bolts

Conclusion

So, There are many different types of rattling noises that can come from many different parts of your engine. Some have simple, low-cost fixes. Others can be very costly.

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