1998 Mercury Sable

1998 Mercury Sable 6 cyl Front Wheel Drive 260000 miles

I seen on the internet that my heater problem might be caused by a vacuum leak and I was wondering where I could download a vacuum diagram for this car
November 21, 2009.

Vacuum leak should have no effect on the heat or heater core
vacuum operate the selection door (like defrost, vent and so on )
very common is low or no heat due to a clogged heater core

have to isolate heater core and flush let me know
and if its the heater vacuum lines that you need let me know
I should have it for you

Nov 21, 2009.
Thank you for that reply but I have taken the heater hoses off of both sides of the heater core and flushed water each way I did get some junk out of the heater core but I had very good flow of water comeing out also.

Nov 21, 2009.
More flushing is needed
try to and soak it with a coolant system flush over an hour or so
you have to have a good flow so you can get the heat

I would isolate the heater core hoses from the engine side
block bypass hose in-between
fill heater core with coolant system flush and let it sit

Nov 21, 2009.