- Rattling noises can be quite hard to diagnose because a lot of damaged or worn-out components can produce the same sound. You’ll want to check the suspension system, the transmission, and the catalytic converter for starters.
- Your vehicle’s heat shield, its timing chain, its exhaust system mounts and brackets, and the hydraulic valve lifter are also possible sources of the rattle. Finally, you can also check the muffler, harmonic balancer, and certain cabin fixtures.
- If your car is rattling, and you can’t find what’s wrong, check for recalls about your vehicle before calling in a mechanic to fix the rattle. It’s always best to have your vehicle checked as soon as possible.
Clicking, whining, clacking, and knocking noises under the hood are a driver’s worst nightmare.
Aside from indicating that something’s wrong, these noises can come from almost anywhere, making them hard to locate.
But what about rattling noises?
My Car Is Rattling Underneath. What Could Be the Problem?
Rattling noises can be quite hard to diagnose because a lot of damaged or worn-out components can produce the same sound.
Fortunately, we’ve compiled a list of the most common parts and systems that are most likely to produce rattling noises as you drive over speed bumps.
Here are the parts and systems you might want to check out.
The suspension system consists of various links, arms, and joints that help the wheels move up and down freely.
Suspension parts work together to provide transverse (side-to-side), up and down, and longitudinal (front-to-back) wheel support.
Over time, components like the control arm bushing, ball joint, tie rod, strut mount, sway bar link, or sway bar bushings can wear out. Once this happens, you might notice that the front of your vehicle produces a rattling noise as you go over bumps.
Diagnosing suspension problems usually involves conducting a bounce test. This involves pressing down on the vehicle a few times and waiting until a similar rattling noise is produced. In most cases, a bad strut is the culprit.
A poorly lubricated transmission can also create rattling noises under the vehicle. Oil starvation can cause metal components to grind against one another, causing them to wear out faster than normal.
For many automatic transmissions, the rattling noise can be heard when the vehicle is moving at low speeds. This could mean that the torque converter is nearing the end of its service life.
For a few manual vehicles, the dual mass flywheel is often the reason why rattling noises could be heard. This sound usually disappears as the driver depresses the brake pedal.
Topping up on transmission fluid usually solves the problem, but if the rattling sound persists, a trip to the local auto repair shop is highly recommended.
After some time, the small chambers or the heat shield inside the catalytic converter can get loose and produce rattling noises.
A clogged catalytic converter can create the same issue, too. Removing any built-up residue inside the cat-con and switching to high-octane fuel usually resolve this issue.
If the catalytic converter starts to make noise, it means that that substrate is breaking away or deteriorating. Once this happens, there’s no other solution other than to replace the catalytic converter.
If the catalytic converter starts to make noise, it means that that substrate is breaking away or deteriorating.–Anthony Harlin, ASE Certified Master Automobile Technician
Keep in mind that the catalytic converter can get damaged even when there are no signs of mechanical damage.
A catalytic converter can also fail due to chemical damage or poison. Because of this, it’s also important to perform a back pressure and rattle test.
The heat shield helps dissipate heat. Once it becomes loose, it can sound like a rattle is under the car or inside the muffler.
A loose timing chain tends to hit the timing chain cover repeatedly, which can sound like a rattle. The noise is also similar to a rod bearing knock.
Exhaust System Mounts and Brackets
Support brackets or mounts in the exhaust system can become loose or rusty after some time. Make sure to inspect your vehicle’s undercarriage from time to time, and see if there are any loose components that need tightening.
Hydraulic Valve Lifter
Rattling noises in the car’s engine can be attributed to a faulty hydraulic valve lifter.
The hydraulic lifter takes up all the clearance in the valve train. When the engine is running at excessively high speeds, a valve float occurs because the engine valves are forced open. This also creates a clearance in the valve train.
The hydraulic lifter then takes up this clearance and prevents the engine valve from closing on the seat.
Hydraulic valve lifters are more likely to collapse in older vehicles.
Metallic rattling could mean that the elements in the exhaust system have become misaligned. It could also mean that there are loose or corroded bracings in the system.
The harmonic balancer dampens harmful crankshaft twisting vibrations. This torsional vibration damper usually consists of a cast-iron inertia ring that’s mounted to a cast-iron hub with an elastomer sleeve.
Heat, exposure, cracks, excessive belt tension, and improper installation can cause the harmonic balancer to fail prematurely. These factors can cause the metal to break away from the rubber and spin off damaging components.
In some cases, simple things like loose objects and cabin fixtures produce rattling noises.
Cups, pens, keys, and other objects can rattle at the same time while you’re driving, making the noise louder than it’s supposed to be.
It’s also possible for internal fixtures like windows, speakers, and fascia to produce the same sound while you’re driving.
What Should You Do About the Rattling Noise?
Before you whip out your wallet and lay down a couple of bills for a local mechanic to do his job, you might want to look into recalls about your vehicle first.
Vehicle manufacturers issue these TSBs to alert affected drivers about a faulty component which they’ll replace free of charge.
Who knows? The rattling noise under your car might be a common problem for those who own the same vehicle.
But in case there aren’t any TSBs for your vehicle, it might be time to bring your vehicle to the nearest repair shop and have a trained professional fix the problem.
Rattling noises while going over speed bumps can mean anything. It can be something simple like a loose bracket or a dirty muffler. It could also be something more troublesome like a clogged catalytic converter or worn-out shocks and struts.
Either way, it’s always best to have your vehicle checked as soon as possible to ensure that the faulty component is fixed and won’t affect the performance of other parts.
Once you’re sure that the rattling noise is a major cause for concern, it’s also a good idea to check for TSBs for your vehicle.
This might save you a couple of dollars and spare you the headache of finding a reputable repair shop in case your vehicle has been recalled due to a faulty part.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.