[Kevin's 2004 CTS]

I have a 1st gen 2004 CTS 3.6 ltr. My water pump recently failed. Today I replaced the water pump with a brand new one. I also replaced all lost coolant with Dex Cool antifreeze. After doing all this I started the car and turned the heat up to the highest level. Upon reaching normal operating temp I noticed it was blowing cold air. I double checked the coolant level which is fine. I than test drove it and noticed the temperature starting to rise, still no hot air coming from heater. I checked the water pump pulley and all is fine with that. I am at a loss. Brand new water pump and coolant level normal but the car over heats with no hot air blowing through heater. Can anyone please offer a suggestion as to what the problem might be? I am at a loss.

 

[Free2reem]

Heater core plugged? Is one hose Going to heater core warm and the other cool ?

 

[Submariner409]

The heater core is full flow at all times; cabin air temp is controlled by blending hot and cold air.

If the HVAC blows cold the most likely suspect is an improperly filled cooling system. All trapped air in the circulating system needs to be bled off. The engine probably has a purge line that runs from a cooling system high point to a fitting on the upper side of the pressurized surge tank - if that purge line or its connector fittings are clogged then the system cannot bleed itself, the water pump cavitates, the engine overheats.

Google something like "cadillac forums cts cooling system purge line" or something close.

https://www.google.com/search?ei=My...&ved=0ahUKEwiEpoGJ4dnnAhXOVt8KHa7RDaAQ4dUDCAs

 

[Free2reem]

The heater core is full flow at all times; cabin air temp is controlled by blending hot and cold air.

If the HVAC blows cold the most likely suspect is an improperly filled cooling system. All trapped air in the circulating system needs to be bled off. The engine probably has a purge line that runs from a cooling system high point to a fitting on the upper side of the pressurized surge tank - if that purge line or its connector fittings are clogged then the system cannot bleed itself, the water pump cavitates, the engine overheats.

Google something like "cadillac forums cts cooling system purge line" or something close.

https://www.google.com/search?ei=My...&ved=0ahUKEwiEpoGJ4dnnAhXOVt8KHa7RDaAQ4dUDCAs

Thank you I’m looking at a car that has this problem looks like it could also be the thermostat what do you think