Ford Repair: 1998 Windstar, engine cooling system, coolant leak

Question
Have 1998 Windstar (GL).  162000 KM.  When should timing belt be changed?  Also steering grinds and front end clunks when turning, is this a rack and pinion problem, had the suspension check and is OK.  One more thing (Yeah I know it's a Windstar)  Heat, from the heater cuts in and out while driving (fan blows fine)  Had the thermostat changed work for 1 month and same problem started again.  Temp guauge likes to go from med to high and back to med while driving.

Answer
Hello and thanks for the question...I'll try to help.
 Which engine do you have in it? If it is the 3.8L there is no timing belt. If it is the 3.0L (Mazda) I recomend that it is changed every 60k miles.
 Have the steering rack checked out for worn tie rod ends.
 As far as the heat goes, do you have a coolant leak? If so...it needs to be fixed first. It sounds like an air pocket is in the engine cooling system. I would recheck the system again and replace the thermostat (again) and go from there. Remember, NEW does NOT mean GOOD.
Hope this helps,
Erik