Knocking sounds from underneath your car while driving could indicate any number of issues, with low engine oil pressure being one common source.
Oil deficiency can leave bearings without sufficient lubrication, leading to carbon deposits and knocking noises. Fixing this issue is easy: simply top-up with more oil!
Loose Suspension Components
As your car ages, its suspension components may begin to wear down. Depending on its severity, this could result in knocking noises under your vehicle when driving over bumps.
Rattling sounds can indicate loose or worn-out suspension parts such as the strut mounts, shock absorbers or control arms that provide smooth ride quality while dampening impactful bumps. When these parts become loose or worn out they can result in metal-on-metal contact that creates a rattling sound when your vehicle encounters large bumps.
Your rattle may also be caused by low oil levels, leading to friction and increased engine wear and tear. If this is the case for you, have your car inspected so a mechanic can clean out any carbon deposits that might be causing issues.
Another cause for clunking under your car could be damaged or worn-out bushings. These rubber or polyurethane cushions reduce vibration and friction but over time may wear down over time, creating excessive clearance that leads to knocks when going over bumps resulting in loud clanks or knocks when driving over them.
Worn-Out Struts Or Shocks
While shocks and struts of your car may not be visible, they play an essential role in providing you with a smooth ride over bumpy roads. Unfortunately, over time these difficult-to-inspect components may wear down over time, so it is crucial that you monitor for any telltale signs they are starting to fail.
If you hear a knocking sound when going over bumps, this could be caused by worn-out or loose struts and shocks. When these components wear out, they cannot absorb road bumps effectively and lead to metal-on-metal contact between road bumps and your vehicle – leaving it unstable and unsafe to drive.
Struts and shocks are usually replaced as a complete set; however, one or both may become worn-out separately. To pinpoint which component is the cause, conduct a simple test: push down on each corner of your car while watching how many times it bounces before coming to rest; if more than a couple times are observed before resting again it could indicate wear on the struts or shocks.
Knocking noises could be due to piston slap in your engine. This happens when a piston hits its cylinder wall due to either insufficient clearance or misalignment issues and hits them, potentially becoming dangerously close. For this reason, it is crucial that any issues be assessed promptly for risk mitigation purposes.
Exhaust System
Your car’s exhaust system is an engineering feat. It serves to manage emissions, lower noise levels and direct fumes away from passengers while at the same time remaining visually pleasing. From the outside it appears as a series of pipe segments running from engine to trunk but each pipe serves a specific function.
One such component is the silencer or muffler, an often-missable part made up of deceptively simple tubes that work to cancel out vibration sounds and keep your vehicle quieter. If this component rusts or develops holes, sound waves will continue to bounce around inside it without being cancelled out and cause increased noise levels from your vehicle.
After the muffler comes a secondary mini-muffler called a resonator that provides additional sound vibration tuning capabilities while significantly increasing exhaust flow efficiency.
The tailpipe serves as the final component of an exhaust system, discharging exhaust gases out the back of most vehicles and away. It may also serve as an aesthetic feature – many modern cars feature chrome-dipped tailpipes.
Exhaust systems become damaged when their pipes come loose and fall beneath your vehicle, such as after driving over rough road or speed bumps where the exhaust has scraped against the pavement or due to damaged exhaust hangers that break off, necessitating repairs from a mechanic, who will either repair it or completely replace the entire system.
Engine Mount Issues
Your engine mounts, like any component in your car, will gradually degrade over time. Rubber material exposed to intense heat and vibrations is likely to eventually wear away over time, rendering them ineffective at absorbing vibrations which radiate beneath your vehicle and leading to loud clunking/rattling sounds that resemble engine knock.
Depending on the severity of an engine mount issue, you could hear sounds when shifting gears or accelerating. If this sounds like your engine, or if there’s any strong suspicion that your engine could be the source, avoid driving your vehicle until seeing a mechanic; continuing to drive with an engine mount issue could damage other components and possibly lead to an accident.
Another potential cause for these clunks could be related to your accessory belt. The belt drives accessory pulleys located throughout your engine bay, and if its tension or one of its pulleys becomes unbalanced or worn out it could produce noises similar to engine knock.
Piston Slap refers to when the piston moves up and down within its cylinder due to clearance issues, producing a knocking sound when changing gears or accelerating. This condition will produce knocking noises when shifting or accelerating your vehicle.
Conclusion
Knocking sounds from under your car can indicate a variety of issues, ranging from simple fixes like low oil levels to more complex problems such as worn-out suspension components, damaged exhaust systems, or engine mount failures. If the knocking persists, it’s best to consult a mechanic to diagnose and resolve the problem before it leads to more significant complications.
