2004 Chevy Impala Heater not blowing hot

Tiny
JSSMITTY
  • MEMBER
  • 2004 CHEVROLET IMPALA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 88,000 MILES
Have a 2004 Impala LS 3.8L. The heater stopped blowing hot recently. Now its to the point it doesnt even blow warm air. Also around the same time this has started happening I have noticed there is an issue with my temp guage. If Im driving the temp guage DOESNT EVEN MOVE. But when I come to a stop and stay stopped just idling for a long while the temp guage comes up into the normal range and hot air starts blowing again. But when I start driving again the temp guage goes back down to near to nothing like the car isnt running and it blows nothing but cool air again. Any suggestions?
Wednesday, January 23rd, 2008 AT 9:53 AM

5 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Souds like a bad thermostat. Change thermostat and flush and fill on the coolant, use 50-50 mix of DEX-COOL.
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Wednesday, January 23rd, 2008 AT 9:56 AM
Tiny
JSSMITTY
  • MEMBER
  • 3 POSTS
I replaced the thermostat the other day. Maybe I got a bad one.I wasnt having issues with the temp guage until I replaced it. Just issues with no hot air. Now I have no hot air (unless sitting still for a LONG time) AND having temp guage issues.
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Wednesday, January 23rd, 2008 AT 1:51 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or do a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also check the thermostat, and the temperature blend door, thats under the dash, in the heater plenum. You can flush this yourself, buy the prestone flush kit and install the tee in the heater return line. Disconnect the heater hose at the waterpump, clamp the hose in back of the tee you installed and back flush till it runs clear.20 mins or so. Bleed air. Either by removing radiator cap, with engine cold, and squeezing the upper hose, and topping off the fluid, or by the bleed valve on or near the t-stat. If it has one.
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Thursday, January 24th, 2008 AT 9:34 PM
Tiny
JSSMITTY
  • MEMBER
  • 3 POSTS
Backflushed it out about 4 times and put another thermostat in it just for good measure. Heat is blowing just fine now and temp gauge is working correctly again! Thanks!
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Thursday, January 24th, 2008 AT 10:10 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Ok Great!
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Saturday, January 26th, 2008 AT 7:59 AM

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