Hi I have had the same trouble with my taxi and it was an air lock in the heater matrix which needs flushing through and bleeding, the worst case scenario is there is a small leak in the head gasket which is putting air into the heater lines.
Richard
October 2009
how do i flush the whole system including the matrix is it a garage job?
shaz
February 2009
Could be the heater controls - check them. Could be a blocked heater matrix. I'd try flushing the entire cooling system including the heater matrix and then refill with fresh antifreeze solution. A lot of gunge and sediment can build up if the coolant has never been changed in 11 years.
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