MCHAccordLX

Hello! I've had my Civic less than a year. I posted here about it last February after I picked it up. Long story short, it had a bad head gasket and the dealership I bought it from decided to replace it for me. It's been a great car over the spring, summer, fall months. However, I'm having some trouble with it when it gets below about 10 degrees (Fahrenheit). It seems to have trouble staying warmed up. I have about a 12 mile commute to work where it will get warm and blow high heat. When I get off the freeway it starts to cool off pretty quickly. The heat isn't as warm (still warm, but not hot). Eventually if I let it sit long enough (this morning was -5) the engine temp needle will start to fall and I gradually start losing heat (the temp of the heat is probably around 60 degrees).
I bought a new thermostat and radiator cap, I'm going to try replacing those in case one is faulty. I figure cheap/easy fixes first. I don't think it could be the head gasket since that has already been replaced.

Am I just being unreasonable with the outside temps and the small engine in this car? Has anyone else experienced the engine temp dropping while it's been super cold out (even after the engine has been warmed up for some time)? Like I said, it's been great all summer, no issues. If I still had a head gasket problem, I figured I would have seen overheating.

Falloutkid90

I have a similar issue on my 03. You may have air in your cooling system and/or your heater core is clogged. I fixed the first one which is pretty easy. Apparently there are two hose on the engine side of the fire wall where the glove box is that are the inlet and outlet hoses to the heater core by unclogging the crap in there and running clr and water through there will fix it.

MCHAccordLX

Thanks for the response, that does make sense. The heater core is probably partially clogged. I bet there may be some air bubbles in there as well. However, with the temperature of the heat coming out of the vents varying, I can't imagine the heater core is completely clogged otherwise I'd be getting no heat/little heat consistently rather than a varying amount? Anything with the heater core seems pretty intense. I'll proceed with the thermostat and radiator cap repair to start, and see if that makes a difference. My guess is probably not, but maybe I'll get lucky.

Falloutkid90

With the air bubbles, i would get geat while i drove and at a stop light it would go lukewarm. Ever since i burped the radiator i havent had any issues with the heat. Try that first before spending money on other things.

MCHAccordLX

That's a good plan. I'll try that. I haven't replaced anything yet because I've been waiting for some (slightly) warmer weather. Last night I drove it around town and it didn't seem to be getting warmed up again until I went on the freeway. When I got off and let the car idle for 15 minutes it held temperature, and I was getting adequate heat (enough that I had to turn it down to be comfortable) while it was just sitting there. I definitely think it's an air bubble or intermittent thermostat.