What Causes a Thud Sound from the Chassis When Starting the Car?

[MaliaMarie]

Car starting with a thud sound from the chassis is due to the aging of certain components in the car's chassis. After a period of use, the suspension system ages rapidly. Some supporting parts gradually lose their original function, causing the chassis to make a creaking sound when starting the car. Below is an introduction to car maintenance: 1. Exterior Inspection: Before driving, check the doors, hood, trunk, and glass condition. Inspect for body damage, tilting, oil or water leaks, etc. 2. Engine and Various Fluids: Check the fastening of engine components and inspect for oil or water leaks at engine joints. Adjust belt tension and inspect the fastening of pipelines and wiring. Top up engine oil, coolant, and battery electrolyte as needed. 3. Tires: Check tire wear and clean the trunk. Replace tires when they approach the wear indicators. Inspect for bulges, abnormal wear, aging cracks, or hard damage. 4. Cleaning and Lubrication: Clean oil stains from the engine compartment cover, door, and trunk hinge mechanisms, and lubricate them. Antifreeze typically has a service life of 2 years and should be replaced during maintenance, along with a thorough cleaning of the cooling system. Due to the hygroscopic nature of the brake system, brake fluid should be replaced every two years.

[McJudah]

I've been driving for almost ten years and have encountered the issue of a clunking sound when starting off several times. The most common cause is loose chassis components, such as aging suspension ball joints or shock absorber mounts, which can rattle when the car accelerates. It could also be a problem with the drivetrain—if the connections on the drive shafts are worn, they may produce a popping sound when subjected to force during acceleration. Additionally, if the brake calipers are sticking, releasing them after being parked for a while can also cause this kind of noise. Don’t take it lightly—first, check if the chassis bolts are tight, then take it to a repair shop for a thorough inspection on a lift. Ignoring such minor issues could lead to suspension failure or parts coming loose, which can be dangerous if they fail suddenly while driving, especially at high speeds where loss of control becomes a serious risk.

[DeJace]

As a car owner, I was startled last month when there was a loud clunk from the chassis during startup. After consulting with friends, I learned that this is usually caused by loose or deformed chassis structural components, such as loose engine mounts causing the engine to shake and hit the frame. Another possibility is wear in the suspension system, where aging ball joints make a creaking noise under the load of starting. I tried checking the tire clearance and felt some looseness when shaking, so I sent it for repair. It turned out to be a small loose bolt, and the noise disappeared immediately after tightening. It's essential to pay attention to these abnormal sounds during routine maintenance; otherwise, they could lead to more severe suspension damage, increasing repair costs and time.

[DianaLee]

Experience tells me that the clunking sound when starting is often due to component issues. Worn ball joints, loose control arms, or failed shock absorber mounting points can cause shaking noises during acceleration. It could also be caused by brake calipers not retracting properly, sticking after prolonged parking, and making a noise when released upon starting. A simple self-check is recommended: listen for the location while revving the engine in neutral. Ignoring this may accelerate component aging and affect safety, so professional diagnosis is advised as soon as possible.