Pronounced clunking from one or more corners of the vehicle, most evident when traveling over uneven, bumpy road surfaces. Handling that is noticeably poor with excessive bouncing over bumps. Although subtle at times, the vehicle may not sit level, sagging at one corner.
Coil springs are exactly what you might picture; large springs at each wheel designed to absorb energy from constantly changing road surfaces as well as severe impacts from potholes and other road hazards. Combined with the strut assembly or shock absorber, these work to maintain tire contact with the road for optimal traction while providing the smoothest ride possible. Considering the demanding load, extreme temperatures, and corrosive substances these components are subjected to, they can develop stress fractures and eventually break. Especially is this true when sustaining high energy impacts from curbs and potholes or when under increased load such as from a trailer.
Spring repair is neither reliable nor safe. Replacing the broken spring is necessary. Considering the factors that lead to a broken spring, it is good practice to assess adjacent suspension components as necessary.