My Car Overheats

jholmes · Joined: 23 Mar 2006 Posts: 81 Location: Eagan, MN

If it's at a normal temp at highway speed its missing the cooling airflow over the radiator in stop-in-go traffic. The fan on a '03 Civic is electrically driven. You need to make sure it runs when the temp comes up. Start your car and let it idle up to normal operating temperature. The fan should kick in at or about normal temperature.

I suspect it's not, so in that case you need to check to make sure power is getting to the fan. If it's not, check to make sure power is getting to the fan relay in the engine compartment. The power to the fan is most certainly through a relay because it draws so much power. If there's a fuse for the fan in the car it's probably just for the temperature switch circuit or the low power circuit controlling the relay, but you can check that also.

This should give you something to do for a bit.

BTW...you'll need a multimeter of some sort to check for power.

2003civic · Joined: 02 Jun 2011 Posts: 4

the fuse has been changed twice and the relay seems fine. The fans kick on when it reaches temperature and they also go on when the ac/heat are on. i drove it around yesterday for over an hour and it never got hot enough to reach mid way on the temperature gauge. i took it to a buddy of mine and he's baffled too. tonight i'm going to flush the radiator and check the cat to see if there's any blockage.

Any other ideas? I appreciate the help

jholmes · Joined: 23 Mar 2006 Posts: 81 Location: Eagan, MN

It still could be the relay sticking occasionally. Especially if it's working sometimes and not others. The relay should be pretty cheap to replace and it would eliminate that. It could also be the thermostat sticking but since you've replaced that recently, I would rule that out.

Otherwise the next time it goes above normal temps, pull over quick with the car still running and see if the fan is running.

Also, I don't know where the radiator is located (height) relative to the engine but there might be a air bleed for it...make sure you've bled any air out of the cooling system if it's required.

2003civic · Joined: 02 Jun 2011 Posts: 4

yesterday when stuck in traffic with my a/c on my temperature gauge went almost up to 3/4's and the fan was running. once i started moving again it went right back to "normal".

my radiator is approx 4in lower than my engine. how would i know if it needs to be bled? when my a/c runs sometimes i don't get cold air out of my two front vents, only the sides near the windows

jholmes · Joined: 23 Mar 2006 Posts: 81 Location: Eagan, MN

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