Hello all,

I have a 2003 Monte Carlo and recently begun having heat problems, it turns on and off but the only time it comes on (not always comes on) is when my RPM's are up. I have replaced the thermostat and still no luck. I do not feel a leak in my floorboards but do smell coolant in the car but I think that is from a previous leaky hose from the radiator to the coolant reservoir that I replaced a week before.

I have seen mention of an air bubble in the head gasket? Is that a difficult complicated repair? And are there any other suggestions of what else may be wrong with it?

Thank you so much for your help! Trying to survive this repair without spending a fortune!

Tom

 

Hey hi, so what comes on when the RPM's go up? Are you saying your heater / fan control switch works? And if the switch is working, your only getting intermittent heat into your cabin? I can ask my mechanic for you, please give me any more specific details and lets see what we can do....

 

I recently had my entire HVAC module out of the car (holds the heater and evap core). It has a small condensation drain. I have not dealt with this on the W-Body (like the Monte), but my expperience has been if you smell coolant in the cabin of the car, it's a heater core (I won't say it's 100% but odds are good). Heater core failures in modern (at least GM) cars normally don't make the carpet wet like older cars did. The coolant will exit the car cleanly from the A/C condesnation drain in the firewall (but because the coolant is essentially leaking "in the car" you will smell it via the air vents).

Here's what you will want to do. First, go to the parts store and get a loan-a-tool of the radiator pressure tester. Pump the pressure to about 13-14 lbs. Look under the car for leaks. If you see a leak near the firewall, try to safely get closer to it. The condensation drain is about middle of the passenger side firewall (can be REAL tough to get a visual of, but if you can also try to feel if it's wet and if you bring a wet hand back from touching it and it smells of coolant, you found your problem).

I hope it's not a heater core, but it's worth inspecting. While using the radiator pressure tester, inspect your hoses and for leaks along with gasket surfaces (listen for hissing sounds, look for bubbling and dripping signs).

 

My 01 Monte carlo.suddenly no heat.temperature gauge going up and down when driving.it could be a few different things?any ideas on what it would be.thermostat maybe

 

[QUOTE=The_Maniac;520595]I recently had my entire HVAC module out of the car (holds the heater and evap core). It has a small condensation drain. I have not dealt with this on the W-Body (like the Monte), but my expperience has been if you smell coolant in the cabin of the car, it's a heater core (I won't say it's 100% but odds are good). Heater core failures in modern (at least GM) cars normally don't make the carpet wet like older cars did. The coolant will exit the car cleanly from the A/C condesnation drain in the firewall (but because the coolant is essentially leaking "in the car" you will smell it via the air vents).


Actually, coolant WILL appear on the passenger side floor when the heater core leaks unless the heater box insulation is in very good condition. It's hard to see it drip because it comes out the seems on the bottom of the heater box, but the passenger side carpet will be damp starting near the passenger side of the front floor vent outlet. Replaced one a couple months ago (Total PIB contortionist act).


If coolant level is low from a heater core leak the heater will blow cool. I suggest checking the coolant level. A leak could also allow air to get into the core causing "air Lock" and lack of circulation.

 

If the temp gauge is responding as it normally did when the heat worked, makes me wonder if the HVAC control panel has failed or an actuator that controls the blend door failed.
But simple place to start, see if you are loosing coolant. If coolant is fine (in the radiator and the overflow bottle) then I would start looking at other possible problems.