1999 Chevy Monte Carlo no heat

JOHNVTOMEY

MEMBER
1999 CHEVROLET MONTE CARLO
6 CYL
FWD
AUTOMATIC
195,000 MILES

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.

Monday, November 17th, 2008 AT 9:45 AM

3 Replies

RENAUDTN

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.

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Monday, November 17th, 2008 AT 6:38 PM

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.

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Monday, November 17th, 2008 AT 8:59 PM

RENAUDTN