The timing belt runs in oil, under its cover, and cannot be seen from outside. Contaminants building up in the oil attack the belt material, so it breaks down early if oil changes are skipped or the oil level drops below the minimum on the dipstick. Fragments of the disintegrating belt end up in the sump and can block the oil pickup, after which the engine is left without oil pressure.

The early signs are a rattle on cold start, slowly rising oil consumption and the oil pressure warning light. The factory replacement interval is ten years or 150,000 miles, but Haynes recommends replacing it at least two years and 50,000 miles earlier. A professional belt change costs more than GBP 2,000, and that is less work than cleaning out the sump, the oil pickup and the lubrication system after the belt has already broken up.

In engines built after December 2019 Ford switched to a timing chain. The water pump is driven by the same belt, so a failure of the water pump bearing can take the belt with it. This is an interference engine, so when the belt snaps the valves and the pistons meet.