I have experienced two engine failures in my 2005 Ford Mustang due to timing chain issues, specifically the failure of the timing chain cassette, guides, and tensioners in the 4.0L SOHC V6 engine. The first failure happened suddenly with no warning, resulting in severe bottom-end damage, including rod knock. The timing chain cassette ends tend to snap off, sending debris through the engine and damaging lifters, camshafts, and other critical components. The second failure was preceded by an audible death rattle, a known symptom of timing chain guide and tensioner failure. Despite this, my vehicle never displayed a check engine light or oil pressure warning before either failure. Unlike later Mustangs with an oil pressure gauge, mine only has a warning light, which never activated.This issue poses a major safety risk, especially at highway speeds. My first engine failure occurred with no prior symptoms, which could have led to an accident had I been merging or overtaking. A failing timing chain can cause misfires, loss of power, or sudden engine shutdown, endangering the driver and others on the road. Independent mechanics have confirmed this issue, and Ford service centers recognize it as a common problem with the 4.0L SOHC V6 engine. Ford has quoted $3,000’$4,000 for timing chain service, making repairs nearly as expensive as engine replacement. These engines rely on multiple chains and hydraulic tensioners that wear out over time, causing slack in the timing chain, jumped timing, and catastrophic damage, typically after 100,000 miles. Despite this, there are no clear warning systems to alert drivers before failure occurs. While timing chains are considered serviceable components, the high failure rate of the timing chain guides and tensioners in these engines, combined with excessive repair costs, indicates a design flaw. I have spent around $4,500 addressing this issue, yet the risk of recurrence remains.