Listen for timing chain rattles (see above). If the engine oil is less than perfectly clean, the oil feed to the timing chain tensioners can block leading to noise when the engine is first started each day. Eventually the tensioners break and replacement is a £2,000 engine out job

Taken from the HJ car by car breakdown.

Having done the same job myself a few years ago you will need to take the engine out not an easy job without ramps in fact I would say almost impossible.It took two of us from Friday morning till Monday night without much sleep never forget it never do it again.I think with hindsight it was probably cheaper to buy a later model Explorer that comes without the timing chain problem.