Hello,
I have a major overheating problem with my 06 Honda Civic Si.

I haven't been noticing it for the past week or so since the gauge is going up to 2/4 max and I was driving on freeways most of the time and in cold weather. I have noticed when i had the car on in idle mode for 20 min and the coolant started boiling. I could just hear it, didn't open up the rad cap though. I have noticed my coolant level in the reservouar is in MIN although i topped it up last week.

One more thing i noticed, the Radiator fan and AC fan are not running at all even when I blast the AC on to max. Checked both relays (20A) in the fuse box they looked ok.
I thought the fan motors gone bad and replaced them yesterday but no signs of live.
How do i find out what is supposed to turn the rad and AC fans on having good working relays and fan motors. What else should I check?

I hope i havn't blown my head gaskets yet.

I have to keep the RPM min at 3000 on the 6th gear to drive at 60miles/hr (100 km/hr) speed. Simular behaviour with lower gears too. I feel like too high rev bt too less torque/horsepower. I think it drives too slow for 3000 RPM at any gear. Could that be due to the overheating problem or it's normal on Si this kind of behaviour.

Any advise from the experts on this problem is very highly appreciated.

Thank you,
Mr.K

 

The radiator fan may not work because the ECT switch is bad.

The loss of coolant is worrisome. Have you detected a coolant leak somewhere? Is there white smoke in the exhaust?

 

Never open the radiator cap when hot, it will boil out and burn you. With the engine cold, take the cap off and make sure the radiator is full to the top. Find out why the fan doesn't work. If they still used ECT switches in '06, that is the first thing to check. It's on the thermostat housing. Unplug the switch and jumper the pins in the plug going to the car. Fan should run all the time the key is on then.

It is normal for the A/C to not engage in cold weather.

 

One thing I didn't see mentionedis the car still under Warranty?

I would check what they said above and I wouldn't keep driving it until you found the problem or else you could really add up the repair bill.

Did you check the oil level to see if coolant got in the oil?

I am not sure where the fan switch is, which most likely is at the bottom of the radiator, but if there is no coolant to heat it up it will not turn the fans on.

 

Thank you for your reply on resolving this issue.

ECT switch? I'm not sure but it sounds like either a WATER TEMPERATURE SENSOR ASSY., which is i think somewhere around Thermostatoranother WATER TEMPERATURE SENSOR ASSY, which is plugged into thebottom part of the radiator.
Any idea which one we are talking about?

I have not detected a coolant leak anywhere underneath and no white smoke from the exhaust at least not when the car is warmed up. But i noticed some water coming out of the exhaust, i thought it was normal all cars especially when the engine is cold yet.

Radiator is full to the top when the engine is cold.

Sinceit is a US car the warranty is void once you export it to another country (Canada in my case).

I recentlydid the oil change, how to i check if the coolant got in the oil and how it possible anyway? Isn't it sealed?

One thing I noticed, i can smell the coolant from the inside of the car, I don't know if it any relevant to this problem or not.

Thank you for your help everybody.

 

Actually if you can smell coolant inside the car then I would say that you have a leak in or near the heater core or, depending on how the hoses are routed one of the hoses could havea leak and it could beseeping in through the firewall. It could just be as simple as a loose clamp.

Have you had to add coolant or water at all to the coolant recovery bottle?

I don't have a manual with me here now but there are two switches, the Coolant temperature sensor, which tells the computer the engine temperature, and the sensor in the radiator which, when it gets to a certain temperature will allow the fans to come on.

You would need to study the manual and check the sensors with either a volt meter or OHM meter, as the manual indicates to be sure they are working correctly.

To check to see if water is in the oil, you just check the oil like you normally do. If it has more oil than you put in it when you changed it, you then have water in your oil. Water will sink to the bottom of the oil pan so you wont really see anything unless the oil color on the dipstick is a grey or milky color. The system is normally sealed but if you blow a gasket somewhere you will get coolant in the oil and possibly oil in the coolant. This could be from maybe.........say......high revs.....or racing!

If you don't think you have the ability to diagnois the problem, you should take it to a radiator shop and have them do a pressure test on the system to see if there are any leaks.
They are also good at finding overheating problems too.

 

Smell of coolant in car may indicate a leak of coolant from the heater core. Inspect under the dash carefully for any moisture.

 

A little update.

I just had my mechanic replace motors for the fan and AC with brand new ones and aslso replaced the rediator sensor.

Here is how it's behaving now:

The the AC fan kicks in when I turnon the heater/AC, so it works as it's supposed to.

But the radiator fan is not kicking in unless I turn the AC on. As soon as i turn on the AC both fans work.

Keep in mind that my dash guage shows the water temperature raises up to2/4 (normal) and doesn't exceed 90 C degrees.
Does that mean my Enghine Coolant Temperature sensor is working fine?

Note: Radiator is full to the top andthe reservoir to max.

After all the work done, so far have not noticed the water boiling up.What should be the coolant tmperaturein the radiator for the rad sensor to switch the fan on?
How can I put it through a test to see if replacing the sensor and motors helped me with my problem?

Very appreciated for your input.

Mr.K