Honda Civic Coolant Loss

-Ok

-And yes, the fan does kick on. The vehicle has never overheated and the temp gauge always stays pegged right in the middle.

Sounds good, thank you!

I had a local Honda dealership look at it yesterday. They ran a pressure test on the AC & cooling system and everything was within spec, there were no leaks and the AC/cooling system is functioning properly. I specifically mentioned items like a head gasket, hose connections, etc. To which I was told they are all fine.

I guess that makes me wonder when exactly the coolant levels should be checked. By the manual levels are supposed to be checked when getting gas (excessive in my opinion) but I've always been under the impression you always check the level in the expansion tank when the engine is cold. Maybe overnight is not 'cold' enough? Maybe I'm not checking the levels at the right time which could explain the disappearance'of coolant?

Don't know for sure if they checked the cap. If they ran a pressure test on the system wouldn't the cap show up as being problematic?

Oh ok, I will monitor the levels and put on a new cap if I continue to lose coolant.

Thanks!

Quick update. I had Honda re-test the cooling system. They said they didnt have the proper equipment to test the radiator cap on it's own but their lead did say that if the cap was defective it would show during a pressure test. I guess they test the system some other way than removing the radiator cap and hooking up the equipment. Everything was holding pressure fine and operated within spec. I was told the coolant level in the expansion tank can vary dramatically and that is pretty normal. I always knew it would go up and down from when the engine is hot to when the engine is cold. But looking at the expansion tank while it's cold has shown the level to drop. Maybe it has to do with the outside air temperature too?

Eitherway, it is documented and even though the powertrain warranty will end this September they said if anything arises after then it would be covered by warranty as the problem has been documented and check twice now before the warranty expired and both times I was told the system is fine.

All of that said, is there any other place to check for a leak?

Ya, puzzled me too. I've never added coolant. Honda has never had to add coolant to the radiator, just topping off the expansion tank. The only time coolant from the expansion tank disappears is after I run the AC. Example: The exapansion tank is at the 'F' mark when the engine is cold. Then, I'll run the A/C for the drive to and from work (a whole 20 mins. The next day I'll check the expansion tank before I start the engine and it is no longer at 'F.' No external leaks, no puddles, and no white crust on any of the hoses or connections. I haven't done the cheical test to see if it is burning off. I'll have to keep an eye on it and may just buy a new radiator cap next week to see if that makes a difference.

A new radiator cap did nothing. I topped off the expansion tank when the engine was cold (first thing in the morning) ran the AC for a grand total of about 15mins. This morning when I checked the levels I noticed it had dropped ever so slightly. Maybe this is normal for Honda? The radiator never lost and coolant and this car has never overheated. It was a certified pre-owned so I feel that if there were any problems it would have been taken care of. Maybe it has something to do with the fact the daytime temperature is 90+ degree outside? I hate to spend so much time on something that doesnt get much use (I hardly ever use AC to begin with, and this problem occurs ONLY when AC is ran). My last guess is maybe its burning off but that seems odd for a car with less than 30k miles.

I should add to all of this that the total amount of coolant it took to top off the expansion tank (from well below the 'Min' line to midway between the 'min' and 'max' line was less than 1/4 cup.

That's what I was thinking too. I'll have to take it to another Honda dealer across town to see what they say.