1999 Chevy Monte Carlo no heat

1999 CHEVROLET MONTE CARLO
195,000 MILES • 6 CYL • FWD • AUTOMATIC
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JOHNVTOMEY
  • MEMBER
  • 7 POSTS
i've changed the thermostat, flushed the system out, put new coolant in, replaced the radiator cap, i thought to change the temp. sending unit. also could it be that i bought a bad thermostat? it seems as though the car has heat whenever it wants. sometimes it works and sometimes it doesn't. i notice that the upper radiator hose gets hot but the lower hose doesn't get hot its pretty much cold. i'm going to try flushing the core. also i do not have any wet spots on the floorboard to indicate leaking core.
Nov 17, 2008 at 1:45 AM
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RENAUDTN
  • ✓Experienced Mechanic
  • 636 POSTS
When you don't have heat you still have air coming out of he vent right?
I'm gonna assume you do:
Make sure you get all the air out of the cooling system, and your level of coolant is good.
Your heater core could be plugged. Install a flush kit and flush your heater core. One way to check is by touching the two heater hoses with car running at normal temp and heat set on high; they should both be very hot. If one is cold or luke warm, clean your heater core.
Also your blend door could be defective or the actuator broken.
Another thing I can think of is a weak water pump.
Finally, if your car has a heater control valve, make sure it's not 'sticky'.
I don't think replacing the temp sending unit would change anything.
Nov 17, 2008 at 10:38 AM
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JOHNVTOMEY
  • MEMBER
  • 7 POSTS
i flushed the core out by taking off both hoses and running water through them. put back together and filled radiator. i bled the air out of the system unscrewing the bleeder screw at the thermostat housing. lost the screw in my gravel driveway though. i got a regular screw and wrapped some teflon tape around it and put it in place of the one i lost. at first it over heated so i left the cap off as i ran the car for a few minutes. put the cap back on and now the heat is nice and toasty. hopefully i fixed the problem. any more fixing and the whole cooling system would be new. thanks for all the help.
Nov 17, 2008 at 12:59 PM
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RENAUDTN
  • ✓Experienced Mechanic
  • 636 POSTS
Glad to hear you fixed it... it's getting cold out there
Nov 18, 2008 at 12:39 AM
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