The Toyota Prius coil springs support the weight of the car and maintain its ride height on the axle where they are mounted. They also let the suspension system move up and down in order to adapt to changing road conditions. Unfortunately, coil springs are vulnerable especially under harsh weather conditions, and when they break, the whole suspension system collapses.
Do not believe the hearsay that broken coil springs is caused by cheaper metal, speed bumps, and overloading. While these may be possible, the truth is that the light, thin component simply doesn't cope well with salt and rust. In fact, some Prius owners have reported rusted coil springs a shortly after buying them in new condition. Most of these cases also stated that aside from the rusting, its paint or finish did not chip at all or flake off.
Other known causes of rusted coil springs include vehicle weight reduction. Car manufacturers have been doing this with their newer models to reduce fuel consumption and CO2 emissions. In order to achieve a lighter vehicle weight, they also redesigned coil springs to be thinner and lighter than before.
To know whether your car's coil springs are broken, take note of the following symptoms:
You'll know that the coil springs are needed to be replaced when you hear a knocking noise from the suspension system whenever you go over bumps. The sound can usually be heard from the rear part of your vehicle.
The component will also show signs of wear or failure when you notice that your car's ride height is low. It's best to always inspect the Prius's rear before you go out for a drive, so you'll be familiar how high your vehicle rides. With this, you can easily notice if its ride height is lowered.
Modern cars, including the latest models of the Toyota Prius, have bigger, wider wheels for better handling and improved appearance. However, this would also mean that the tire sidewall is much closer to the suspension system than before. So if a coil spring breaks, there's a chance that one of the rear tires will suffer collateral damage.