Is It Normal for the Chassis to Get Scratched?
3 Answers
During the design phase of a car, the chassis is built to withstand a certain level of impact. The most vulnerable parts of the car's chassis are various pipelines, such as brake hydraulic pipes and fuel pipes. However, these pipelines are concealed and protected within the grooves of the chassis steel plate, not protruding above the chassis's horizontal plane. If, as you mentioned, the chassis encountered a step, which is a flat obstacle, the steel plate of the chassis would make planar contact with the step. In this scenario, the pipelines hidden in the grooves of the steel plate would remain undamaged. On the other hand, if the chassis collides with a protruding stone on the ground, the contact surface would be point-like. The protruding stone could potentially hit the pipelines within the grooves, leading to oil or fluid leakage, which poses significant risks. It is advisable to drive your car to a repair shop and have the chassis thoroughly inspected by lifting the vehicle. If the pipelines are undamaged and only the steel plate has suffered scratches, applying some paint to prevent rust would suffice. However, if the pipelines are damaged, a comprehensive inspection and repair are necessary.
Scraping the chassis is actually quite common, especially when novice drivers pass over potholes or speed bumps in sedans. Once when I was going down a steep underground garage ramp, I heard a screeching sound, and upon checking, found a large scratch on the chassis guard plate. However, the key is to look at the scraped area. Important parts like the radiator bracket, fuel tank, and fuel lines must be dealt with immediately if scratched, otherwise there's a risk of oil leakage or even spontaneous combustion. Scratches on ordinary plastic guard plates aren't too much of a concern, at most affecting the appearance. I recommend drivers who often travel on rough roads to install a chassis guard plate—a resin one will do, as it's even lighter than the original metal plate, so you won't have to worry about your car the next time you hear that screeching sound.
From a repair perspective, most undercarriage scrapes are considered normal wear and tear. Recently, I worked on a car where the skid plate was punctured by a rock, causing coolant to gush out. Honestly, there's no need to panic over plastic component scratches—what you should be wary of is the metallic clunk sound when bottoming out. Particularly around the engine oil pan area: an aluminum oil pan dent can easily lead to oil leaks, and on turbocharged cars, a bent oil line might cause insufficient oil supply. I often teach car owners this self-inspection trick: after parking, press on the exhaust pipe to check for looseness, pop the hood to sniff for gasoline odors, and peek underneath for any reflective fluids. As long as the three major components (engine, transmission, chassis) are unharmed, treat those scrapes like battle scars—consider them your vehicle's badge of honor.
