2000 Mercury Sable heat is warm not hot

Tiny
CLINE07
  • MEMBER
  • 2000 MERCURY SABLE
Heater problem
2000 Mercury Sable Front Wheel Drive Automatic 90000+ miles

My heater will get warm for a minute or two, then it gets cold. I have changed the thermostat and checked the hoses for blockage. How do I check the door to the warm/cold controller?
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Sunday, December 6th, 2009 AT 3:25 PM

3 Replies

Tiny
BMRFIXIT
  • EXPERT
If you open the hood and check by the firewall you will notice two heater hoses going into the firewall and connect to the heater core
this is a common problem that I've seen and is the heater core need to be flushed
for start
Check coolant level
Is the car reaching operating temp
Check heater core hoses if both are hot,
if both hoses hot and not enough heat inside suspect blend door actuator
if not one hose hot and the other warm or cold the heater core need to be flushed (very common)
as a 1st step
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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Sunday, December 6th, 2009 AT 3:51 PM
Tiny
CLINE07
  • MEMBER
I flushed the heater core but didn't pinch the bypass hose. Not sure where this is? The heater is working better, it blows warm air as long as the rpms are 2 or higher but blows cold air at 1 rpm and lower. Could this still be the heater core? Thank you for the quick response.
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Tuesday, December 15th, 2009 AT 4:46 PM
Tiny
BMRFIXIT
  • EXPERT
Try and flush it again
and it should get better
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Tuesday, December 15th, 2009 AT 6:54 PM

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