Answer
FORD OHC TIMING BELT REPLACEMENT RECOMMENDATIONS 1.3L Aspire - 60,000 miles
1.6L*, 1.8L, 1.9L Escort - 60,000 miles
2.0L diesel (1984-'87) - 60,000 miles
2.0L SOHC Escort & Tracer (1999) - 120,000 miles
2.0L SOHC Focus (2000 & up) - 120,000 miles
2.0L Contour - 60,000 miles
2.0L* Probe (1989-'97)- 60,000 miles
2.0L* DOHC (1999 & up all models) - 120,000 miles
2.0L 4-cyl Ranger pickup - 60,000 miles
2.2L* Probe - 60,000 miles
2.3L 4-cyl Ranger pickup - 60,000 miles
2.3L Mustang & T-Bird - 60,000 miles
2.5L 4-cyl Ranger pickup - 60,000 miles
2.5L V6 Probe - 60,000 miles
3.0L V6 Mercury Villager (1993) - 60,000 miles
3.0L V6 Mercury Villager (1994-1998) - 105,000 miles
3.3L V6 Mercury Villager (1999-2002) - 105,000 miles
3.0L V6 Taurus - 100,000 miles
3.2L V6 Taurus SHO - 100,000 miles
(*) - Indicates an interference engine that will suffer valve damage if the timing belt fails. As you can see the 4.0 is not listed as being OHC. This would indicate that it does not have a belt to replace so therfore it is not interferance. My advice would be to call the dealer to verify this.
All Mercury Villagers are NON interference engines (same as Nissan Quest engine), made so at the express demand of Ford who assembled them, and who wanted no repeat of the Escort problems and costs of the 1980's when interference engines caused severe damage when timing belt broke. Many sites around the internet, including a few parts/replacement sites, incorrectly state the opposite. See most Groups (like Yahoo) on Villager/Quest for clarification.
Just because an engine doesn't have a timing belt doesn't mean the engine is not an interference engine. The 4.0L SOHC is an interference engine, if the timing chain breaks or the tensioners fail there will be major damage to the engine.
------------ZX2Fast-----------It should be noted that all Zetec engines (2.0 DOHC) are NOT interference engines. They are listed as interference in most tech manuals but this is wrong. All Data recently corrected this mistake. There are deep reliefs cut into the top of the piston to clear the valves when they are fully extended. There will be no valve damage if the timing belt breaks on a Zetec engine.