Turn the ignition to ON and then turn the heat all the way up; otherwise the heater valve doesn't open. Then turn the ignition off before the drain.

 

Today I did drain the coolant and filled it with new Honda spec Type 2 coolant. In fact I followed the instructions in the official Honda shop manual. After the fill, the manual specifies that the radiator cap should be installed loosely, the engine started and warmed up (the radiator fan should come on at least twice). I noticed that the engine temp kept going up beyond the half way mark. I thought that was unusual because prior to the coolant change, the gauge stabilized at 1/3 the max of the scale. The fan did not even come on once. I turned on the heat to see it would make any difference. It didn't. I felt the engine was warm enough, at least the upper hose was warm to touch. I shut off the engine and let it cool. I noticed that some coolant from the overflow jug had already been sucked in to the radiator. Also, the coolant was low in the radiator. So I added sufficient coolant to the radiator and also topped off the overflow jug to the Max mark. Then I took the car for a test drive. I noticed that the temp gauge kept going up, beyond the half way mark. By the time I got home, the gauge was very near the red line. Very upsetting. I have now let the engine cool. I noticed that the overflow jug coolant was still in place, but I had to add some coolant to the radiator to fill it to the neck. I'm just wondering if there is a leak. Tomorrow I'll check if the drain spigot is tight enough. Any other ideas? Any reason why the fan didn't come on?

Anup

 

My guess is there is still a lot of air in the cooling system. It may also be affecting the radiator fan switch at the bottom of the radiator. (Also, check that it is not unplugged.)

Fill the reservoir and the radiator. Then this time leave the radiator cap off to purge air from the system. Use a funnel. You may have to gently rev the motor a little while it is warming up to get the thermostat to open up. Most of the air purging happens after the thermostat opens.

You can carefully feel the lower radiator hose, when it gets hot almost like the upper radiator hose, the thermostat has opened.

 

I just replaced my radiator on a 2007 and had a similar experience. It seemed to be a combination of low fluid and I assume air. I filled the radiator and the reservoir left the cap loose. Ran the engine fan never came on temp gauge got about 3/4 of the way up. Engine cooled overnight it sucked down what was in the reservoir. Filled up the reservoir again ran the engine with the cap loose started to overheat the fan would come on though but it never ran long enough to cool anything. Engine cooled overnight again sucked down the reservoir. Third time added more antifreeze to the radiator and more to the reservoir. Ran again fans did come on finally engine did not overheat. I did have to run the engine at about 2k rpm to get the engine to heat up.

Check the reservoir again tomorrow I suspect it may be empty.

 

Haven't done it yet on my Accord, as it is new, but the way I've done it on other cars is disconnect the lower hose from the radiator, everything comes out. Have cap off. Heat on, engine off. (I hope I really didn't need to say that.) Drain the overflow reservoir. Fill radiator and overflow reservoir. Start car cap off, heat on high. Watch level, keep adding. Takes 15 to 30 minutes.

 

I checked both the fan electrical connections. They were both intact. The connectors are by the side of the fan bodies.

I did refill the radiator and left the cap off. I started the engine. The coolant level in the radiator kept rising till it started spilling out. Maybe this is a good sign? At that point I shut off the engine and put the cap back on again. I restarted the engine. For periods of time I revved up the engine to 1500 rpm (the steady state is close to 1000 rpm approx). I also turned on the heat to full blast. Maybe this is a good sign? The temp gauge held steady at 1/3 of the max scale, like I'm normally used to seeing. Both the upper and lower hoses were warm. After running the engine for 10 - 15 minutes, I shut it off. I didn't see the fan come on. When the engine cools down, I'll check for the coolant level in the radiator and the recovery reservoir.

 

The radiator fan switch is located at the bottom of the radiator.

When you left the radiator cap off and coolant first started coming out, you should have let it run longer with the cap off to let more air out. It usually takes somewhat longer for most of the air to purge out. You would just keep topping off as the coolant level drops during the purging process.

However, since the coolant temperature seems to have stabilized in the normal zone, the system should purge out air during normal driving, as the air collects near the radiator cap and may be purged out through the hose to the reservoir. For the next few days, when the car is cool, check the reservoir level and top off as necessary.

Although it can be done without it, I use a Lisle spill-free funnel to make the air purging process easier.

 

Redbull, after the cool-down, I saw the levels in both the radiator and the overflow jug had dropped. I added more coolant. This time I took the car on the road and drove it a couple of miles. The temp gauge has held steady at less than half way mark. Just for the heck of it, I turned the A/C on. At that moment both the fans came on. Does this prove that the fan switch is working or is that a different switch? In any case, the temp gauge stayed steady with the A/C on. I let the engine cool again. The level in the overflow didn't drop again. I'll take it for another test drive tomorrow. It is too late to use the Lisle spill-free funnel now, but I'll try it the next time.

 

When the A/C is on, both fans will run; but, not because of the radiator fan switch.

You probably are okay. It does take quite a bit before the radiator fan switch triggers both cooling fans to run. When the coolant temperature at the radiator fan switch is above 196 degrees F, it suppose to trigger both fans to run.

The thermostat starts opening around 169 - 176 degrees F, and is fully open at 194 degrees. Therefore, if the cooling fans were to be trigger by the radiator fan switch, it should happen after the thermostat has opened. Also, the cooling fans usually don't run too long before the coolant temperature drops.

Just watch the temperature gauge and check the coolant level for the next few days.

 

Redbull, thanks for explaining what triggers the fan. I'll try to locate the radiator mounted fan switch this weekend.

This morning the coolant levels had not dropped. I took the car for a test drive, half of it on the highway. The temp gauge held steady below the half way mark. I turned on the A/C, the gauge held steady. After the engine had cooled, the level in the overflow jug had not dropped. I'm taking it as a sign that all air has been purged or nearly purged. I will continue to keep an eye on the gauge, and will continue to carry the coolant jug with me in the car, just in case.

Concerning the Lisle funnel, what happens if you keep adding the coolant. After all the air is purged, eventually some of it will remain in the funnel. Will there be a spill when the funnel is removed?

Anup