Honda Civic Coolant Loss

Pressure test the cooling system with a coolant pressure tester that will find any loose hose clamps etc.Also you could have a inop a/c condenser fan?Do you ever hear the a/c condenser fan kick on? this guide can help us

https://www.2carpros.com/articles/car-is-leaking-coolant

Please run down this guide and report back.

-Ok

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

Ok lets start with the pressure test also lets pressure check your radiator cap it could be venting off coolant at a lower pressure the what its supposed to.Let me know wha you find and we will go from there.

Sounds good, thank you!

Your welcome keep me posted.

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?

If the egine sits over night that would be cold or it sits long enough for the temp gauge to not go up when the key is on.The main reason to check it cold is safety so you dont get hurt by the hot coolant.Also the coolant isnt all expanded like when its hot.Is there a hot line or cold line on your coolant tank or both?Your manual is correct you should check fluid levels every time you need fuel.It does sound excessive but think of it this way if you develop a coolant leak transmission leak or start burning oil you can possibly catch it early before you do any major damage.Rather then throw caution in the wind and check your fluid levels when ever.So did honda also check the ruadiator cap a lot of guys just dont even think about checking that they check the rest but dont even bother with the cap.

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?

No because you remove the cap and put the pressure tester adapter on the bottle and hook the tester to the bottle without the cap.The cap has a seperate adapter to test seperately. Thats why i said the cap is usually over looked.If you keep loosing coolant you could always just replace the cap to see if it that helps the caps are pretty cheap.

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

Thanks!

Your welcome keep me posted on what you find in case we have to keep looking.

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?

To test the cap inline while doing the pressure test doesnt make sense because how would you know if the cap was leaking or you just had a leak in the system.I have never heard of pressure testing a cooling system with the cap i have only seen the pressure hose go on where the cap goes that is where you add the pressure.Then a seperate adapter connects the cap to the pressure tester and makes sure it vents at the proper pressure and holds the pressure.The coolant level will get higher when the coolant is hot from expasion and go down when its cold.But you shouldn't have to keep adding coolant though have you had to add and coolant since we last talked?Another crazy thing is the stant coolant pressure tester i have you pressure test the coolant cap and the cooling system seperate pretty sad the honda dealer cant do that with all there factory tools they have cant pressure test your cap.If you have ruled out the cap?Also any outside leaks and are still loosing coolant its a small leak external or your burning it in the engine which there is a chemical tester to test that.

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.

Keep in mind with the a/c on it will run hotter and you could have a bad cap.Caps are pretty cheap so that would be a cheap thing to try.Keep me posted on whats going on with the car.

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.

You could just have a very small that honda didnt see just keep an eye on the coolant level.You shouldnt have to add coolant just to use the a/c.

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

I would keep me posted on what you find.

I have this scheduled for Wednesday for the other Honda dealer in town to look at it. After describing the problem to a service advisor I was told all they would do is a pressure test and if that doesn't show anything then they would do a leak-down test. I wasn't familiar with a leak-down test but after looking it up I don't see how that would show coolant loss. You had mentioned a chemical test could be done to see if it was burning off. Is that something a dealer would have to do? And with the small amount of coolant I am losing would you say it's more likely a loose connection?

Thanks again for all of your help.

A leak down test is usually used to find a compression loss i guess they would look for bubbling in the coolant while doing the test..The chemical test they rent them at auto zone you just have to by the chemical which is about 8 you could do that yourself.I would think its connection somewhere but anything is possible.

Hey I wanted to know if you ever found out what cause your leak on your Honda? I may have the same problem too

I never found out what was causing the leak, though it no longer leaks coolant. I've run AC/Defrost pretty regularly the last several months and there has been no drop in the coolant overflow tank level.

I tried a new radiator cap and that didn't make a difference. If you haven't already try reading the previous replies.