Car Heater Issue

I have a 2005 Hyundai Elantra with arund 73,000 miles on it. When I’m driving my heat works awesome, but as soon as I’m idling at a stop light it goes much colder. If I have been running the car for a longer period of time the heat doesn’t go as cold, but it is still noticeable cooler than when I’m actually driving. What could be casing this???

This sound like a coolant circulation problem. First thing, check the coolant level to make sure it is not low. After that could be an air bubble in the system or a water pump problem.

Do you think it could be a thermostat issue? Or does this sound like strictly a coolant/water pump issue?

Check the coolant level first. It’s free. I doubt it’s a t’stat issue.

No. It sounds like your coolant is low …as was said. If it was a stuck open thermostat, you would lose temp with the ram air. You would have it return idling, if it produced warm/hot air at all.

Okay. So IF the coolant is low, do you think it is most likely the water pump? Or could be the radiator?

There are many places that coolant could leak from. You don’t want to throw parts at it. You need to examine (or have someone examine) the entire cooling system closely to find any leaks. You/they may have to do a pressure test too.