I've only had this car a few days (use to have a TL). When I'm at a long stop light, after a few minutes the temp quickly moves up to about 3/4. It just stays there as long as I'm idling. As soon as I start moving it quickly drops down to normal again. Any ideas? Is this harmful to the engine? Both fans are operating.

 

Change your thermostat! I had this same problem a few weeks ago. Also look at your antifreeze reservoir and make sure the cypher hose is connected to the lid. I went ahead and emptied my out and filled it with all fresh coolant.

 

check water pump as well it might be on its way out

 

May just be air in the system or a faulty radiator cap. Try the easy things 1st. Burp the coolant & top off, replace the cap & go from there. Google it. The procedure is basically the same for most cars.

 

Is this with your a/c on? My car does it sometimes when the a/c is on if it's really hot and i'm sitting still

 

Probably due for a coolant change anyways. Might as well do that while you're at it.
My car used to do that until I figured that only 1 fan was kicking on instead of 2.

 

Got a thermostat and cap and going to flush system tomorrow. Internal reservoir pipe is intact and both fans are functional. I'll update when done.

 

I replaced the thermostat and cap and flushed the coolant. I also noticed that what appears to be a temperature sending unit in the thermostat housing is broken. The plastic part that holds the plug is broken off so the plug does not stay plugged. Does anyone know what this part is called or what it does?

 

Coolant temp sensor I think. You can buy them fairly cheap.

 

Looks like the broken piece is the fan thermo switch. It is located on the thermostat housing. Sounds like it tells the fan when to cut on and off. Not to be confused with the temperature sending unit on top of the water pump.

 

x2

are u low on coolant? i'd check for coolant leaks,

 

my bad didnt read last post...i work at advanced we sell those for cheap, go to the website and buy it. google some coupons to save some money

 

Still haven't solved problem. I replaced both the sensors/switches that are in the thermostat housing, the thermostat, rad cap, and flushed and burped the coolant system. I am still occasionally overheating and loosing coolant. I can't see any coolant leaking anywhere but when it overheats I can smell coolant (outside car). I recently drove from San Antonio to El Paso (8 hr) and back. I had to pull over every few hours and add a quart or two of coolant to avoid overheating. There is no water in oil. How can I tell if water pump is leaking or bad? What else can it be?

 

Seems like it's your headgasket. Just be sure to check your coolant level quite often to prevent overheating.

 

If it is head gasket how can I confirm that?

 

Does anyone know how to tell if my head gasket is where I'm slowly losing coolant? Thank you.

 

Most places should be able to test the head gasket and see if that really is the issue. But otherwise some symptoms could be oil in the coolant or coolant in the oil. Also a smell of coolant coming from the exhaust.

If you ever notice, when the car is cold, that your radiator is low on coolant but your reserve tank is quite full, that could be another giveaway on it being the head gasket.

 

I don't have oil in coolant or vise versa, but other symptoms sound accurate.

 

I would have a compression test preformed on the motor, and have the cooling system pressure tested. If you are overheating and having to add coolant like you are there is either a pretty good leak or a blown gasket. The fact your fan switch was broken leads me to believe that you may have started to overheat one time due to the fan not coming on and have a bad head gasket/warped head.

 

How much do these tests typically cost?

 

You need to find a competent Honda specialist.

Sorry to say, but you should have brought this problem to the previous owner's attention back in September as soon as you discovered it. (That's why he got rid of it...?)

 

It was the head gasket. I can't afford to do the head gaskets. I know it's not the best scenario but I decided to use Blue Devil Head Gasket Sealer. I found a lot of people who said if the leak is small and it is used exactly as directed it will work. Fortunately it worked. I've been driving for a week now and no leak. I will replace the head gasket eventually but this bought me some time.