Run car until hot engine temperature. Remove water resevoir cap, slowly and carefully air bubbles will come out, with some hissing. Leave until cool then add water/coolant mixture to resevoir. Cause is possible air lock, this cured mine. (Rover45 2001)
Helper
September 2009
I have a Rover 45 and the heater is blowing cold air not hot, grateful if you could tell me what the problem is?
Louis
December 2007
Solved this problem on my Mercedes 190 E simply backflush the heater matrix. That is to say run cold tap water through the heater matrix against it's normal flow. There's a thread on this on the mercedes190.co.uk forum called (190 Car Heater, And Heater Matrix Problems, Step by step possible solution.) this thread suggests using caustic soda to help loosen gunk, don't always need to though, simple back flush under tap pressure usually suffices.
Julian Cox
December 2007
make sure that the water resevoir is full (if it runs low water cannot get into the heater matrix) other than that it could be that the heater matrix is blocked or the thermostate is faulty (if the car is over heating i would imagine it is the thermostat)
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