I have a one month old to me 2005 civic coupe . At first I noticed a very slight antifreeze smell when the engine got warmed up. I have notice 2 very intermitent problems. First occasionally I would not have any heat. The temp gauge would be normal and the fan would blow, but the air was cold.

Second, twice now I have had a temp gauge peg hot. I replaced the engine coolant thermostat two weeks ago (genuine honda) after the first case of overheating. I took a 600 mile trip right after the replacement and had no problems. A very slight hot antifreeze smell when I finished the first half of the trip and only had to add 1 to 2 ounces of antifreeze.

Yesterday I had a much smaller trip of 120 miles. All of it was highway except the last 8 miles which was stop and go. Each time I stopped at a light , the temp gauge would go from normal (just below half) to all the way hot within 20 seconds. As soon as I would start to move again, the temp would drop very quickly to normal. The outside temp was about 45 degrees.

Today I checked the antifreeze level and it was only an ounce or two low which surprised me since I could see a very slight amount of coolant on the ground under the battery area.

After adding the very slight 1 or 2 ounce of coolant, I drove the car on an errand and when I got home let the engine idle. Both large radiator hoses were hot, no coolant leak noticed , and the coolant fans came on when the temp gauge reached one half.

Is there an air bleed on the cooling system as on older civics I have had in the past that I am overlooking and have air trapped in the system? I am adding coolant on a cold engine directly into the radiator. Mileage is 80000.

Would appreciate any ideas on these intermittent problems. No heat and overheat.

jeff

 

So no one has any ideas????

 

I don't think there is a bleed bolt on Civics 1996 and newer. You just let the engine idle for like 15 minutes (or until all the air escapes) with the radiator cap off.


Sounds like your radiator fan might not be working. This would explain why the engine cools back down once you get moving.

 

It seems like it never overheats at highway speed, so Like Trust said, the fans may not be working consistently when they should. Also they come on through separate mechanism when you use the A/C compared to when the engine heats up (Thus, paradoxically, turning on the AC could cool off the engine by starting the fans). I think the 2005 still has a thermal switch on the thermostat housing. On older models these switches were well known to stop working and cause overheating in traffic. If that's the case you can unplug the switch and hot-wire it so the fans run all the time, then test drive.

The other thing you could do is next time it heats up, simply get out and check whether the fans are running. Be careful as major engine damage can occur suddenly due to overheating.

 

iv had the same problem with my civic,

its more than likely one of two problems.. the water pump or the radiator.. on the 05's i would lean more toward the water pump and go ahead and replace the timing belt while your at it, if thats your problem..