My heater blows cold air and the engine temp gauge went all the way to the top then quickly down when I turned the heater off. What could it be?

Minerva Torres

Asked by Dec 09, 2013 at 09:52 AM about the 2005 Honda Civic EX

Question type: Maintenance & Repair

Per the boards, I topped off coolant and drove it around yesterday with no problem but this
morning it did the same thing - blew cold air out the vent and the temp gauge went all the
way up then to regular level when I turned the heater off.  It's 4 degrees out so I need the

3 Answers


I had the same issue with my Acura Integra (very similar to the Civic) which came from a hose that was leaking, which caused an air bubble to form in the system. The temp gauge registered "all the way hot" because it was in air, and not in fluid, so it didn't know what to do. I would guess that it's likely you are also leaking coolant and have an air bubble in the system or your heater core is clogged up. I had another similar problem in another older car, and it ended up being coolant that didn't have enough anti-freeze to keep the system from freezing up. I had a vehicle that was running and producing heat, but I had an ice clog in the hoses coming into the heater core. I'm guessing in your situation though that you're leaking/loosing coolant somewhere and that's causing an air bubble. Keep the coolant topped off and get it to a reputable mechanic for them to check out. You're not the only one with this issue with the cold weather :)

5 out of 5 people think this is helpful.
Minerva Torres

The mechanic can't recreate the problem. I had already checked the coolant and had added some. He added some too. We'll see what happens last time I said there was something wrong with my car, he wouldn't believe me until after the drive test when he heard the noise I had reported. Thanks for your answer Woolley. I think it was an air bubble.

2 out of 2 people think this is helpful.
Rizza Camille Cañete

Thank goodness a response that actually makes sense. I've been checking the internet for this problem and people posted some different trial-and-error solutions. I have an '04 civic and it has always acted up like that during cold weather 'ESPECIALLY' winter. I decided one day to just fill up the coolant and that actually worked for a while - worked in a sense that the gauge doesn't go MAX. But it still pumped out cold air. Now, I get it why whenever I open the hood there is a leak of liquid - likely the coolant! Your answer makes sense, thanks! I will have this checked up soon!

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