Honda Civic Coolant Loss

Tiny
GOLDENDAVE
  • MEMBER
  • 2007 HONDA CIVIC
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 28,000 MILES
I have a 2007 Honda Civic LX with 28K Miles. When I run my AC I notice the next day that the coolant level in the expansion tank has dropped slightly and does not rise. This happens ONLY when I run AC, otherwise there is no coolant loss. There are no puddles, and the coolant is not in the oil so I have no idea where it could be going. I'm thinking maybe one of the hoses is not tight? What else should I be looking at?
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Monday, July 18th, 2011 AT 6:58 PM

24 Replies

Tiny
SATURNTECH9
  • EXPERT
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 condensor fan?Do you ever hear the a/c condensor fan kick on?
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Monday, July 18th, 2011 AT 7:06 PM
Tiny
GOLDENDAVE
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-Ok

-And yes, the fan does kick on. The vehicle has never overheated and the temp gauge always stays pegged right in the middle.
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Monday, July 18th, 2011 AT 7:09 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Monday, July 18th, 2011 AT 7:23 PM
Tiny
GOLDENDAVE
  • MEMBER
Sounds good, thank you!
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Monday, July 18th, 2011 AT 7:28 PM
Tiny
SATURNTECH9
  • EXPERT
Your welcome keep me posted.
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Monday, July 18th, 2011 AT 7:33 PM
Tiny
GOLDENDAVE
  • MEMBER
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?
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Tuesday, July 19th, 2011 AT 2:40 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Tuesday, July 19th, 2011 AT 4:53 PM
Tiny
GOLDENDAVE
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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?
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Tuesday, July 19th, 2011 AT 5:24 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Tuesday, July 19th, 2011 AT 5:47 PM
Tiny
GOLDENDAVE
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Oh ok, I will monitor the levels and put on a new cap if I continue to lose coolant.

Thanks!
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Tuesday, July 19th, 2011 AT 5:51 PM
Tiny
SATURNTECH9
  • EXPERT
Your welcome keep me posted on what you find in case we have to keep looking.
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Tuesday, July 19th, 2011 AT 5:57 PM
Tiny
GOLDENDAVE
  • MEMBER
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?
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Friday, July 22nd, 2011 AT 8:43 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Friday, July 22nd, 2011 AT 9:09 PM
Tiny
GOLDENDAVE
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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.
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Friday, July 22nd, 2011 AT 9:40 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Friday, July 22nd, 2011 AT 9:45 PM
Tiny
GOLDENDAVE
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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.
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Friday, July 29th, 2011 AT 1:55 PM
Tiny
GOLDENDAVE
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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.
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Friday, July 29th, 2011 AT 1:59 PM
Tiny
SATURNTECH9
  • EXPERT
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.
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Saturday, July 30th, 2011 AT 3:22 PM
Tiny
GOLDENDAVE
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That's what I was thinking too. I'll have to take it to another Honda dealer across town to see what they say.
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Saturday, July 30th, 2011 AT 3:28 PM
Tiny
SATURNTECH9
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I would keep me posted on what you find.
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Saturday, July 30th, 2011 AT 3:37 PM

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