2000 Mercury Sable Heater blows cool air

Tiny
RENFROST84
  • MEMBER
  • 2000 MERCURY SABLE
Heater problem
2000 Mercury Sable 6 cyl Two Wheel Drive Automatic

When the car is moving, the heater works and warms just fine. When I am sitting at a stop light or moving under 20mph, the heater blows out cool or cold air? Do you know what could cause this?
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Thursday, December 10th, 2009 AT 3:32 PM

1 Reply

Tiny
BMRFIXIT
  • EXPERT
Check coolant level add if needed
if coolant is OK

Heater core need to be flushed
isolate heater core plug bypass hose and flush heater core

these are the steps
WARNING: NEVER REMOVE THE PRESSURE RELIEF CAP UNDER ANY CONDITIONS WHILE THE ENGINE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN DAMAGE TO THE COOLING SYSTEM OR ENGINE AND/OR PERSONAL INJURY. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE COOLING SYSTEM OR DEGAS BOTTLE, USE EXTREME CARE WHEN REMOVING THE PRESSURE RELIEF CAP FROM A HOT COOLING SYSTEM OR DEGAS BOTTLE. WAIT UNTIL THE ENGINE HAS COOLED, THEN WRAP A THICK CLOTH AROUND THE PRESSURE RELIEF CAP AND TURN IT SLOWLY UNTIL PRESSURE BEGINS TO RELEASE. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN CERTAIN ALL PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE PRESSURE CAP (STILL WITH A CLOTH), TURN AND REMOVE PRESSURE RELIEF CAP.

Engine cool

lower the coolant level

Locate the two hoses running to the heater core
disconnect them at the engine side leaving hoses connected to heater core throw the firewall
make sure you pinch and close the bypass hose between the two heater hoses
use garden water hose and compressed air if possible
run the water and follow by air throw one side and out the other and vice versa
do that two to three times watching what leaving the heater core you are looking for the good flow and clear water to run throw
reconnect hoses
top off coolant system
good luck
let me know
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Monday, December 14th, 2009 AT 8:17 PM

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