Coolant in tank below minimum line when cold, but doesn't decrease over time

[MichaelB450]

This has been an issue with my car since I had it new. Basically the coolant in the tank is always below the minimum line, but it goes up to the minimum line when the engine warms up. The level stays at around half way below the minimum line and the bottom of the tank when the engine is cold. I actually took it to my local Honda service center when I first found the issue and they filled up the coolant tank all the way to max and sent me on my way. The service guy saw the level and I did ask if that was rather normal, and he said it is (which I sort of doubt). When I got home I checked the engine bay and noticed that coolant came out of the overflow pipe on my 10 - 15 mile drive home.

I did notice that the level was at about 2 inches from the bottom of the tank last weekend and the engine bay was very cold, like I could feel very cold air radiating from the engine bay when I opened the hood. Once I started the car and let it warm up for about 2 minutes, the coolant level went back the level it usually is. I always look in the engine bay for any signs of leaks and I can't find anything obvious, and it doesn't smell like coolant anywhere. On cold starts there is white smoke coming from the exhaust pipe, but that clears up pretty quickly (no more than a minute). No white smoke from the exhaust on evenings either.

I am getting a bottle of genuine coolant from my local Honda service center on Saturday, maybe earlier if I really need it. It's always good to have spare coolant available at home. I will top the level to minimum when the engine is completely cold and monitor the level over time. Cause for concern, or is it really normal as the Honda Service guy told me?

Edit: Just went to check for any coolant leaks, still looks good. I took the radiator cap off to take a quick smell of the coolant in the tank (to know what I am smelling for) and the coolant level went from 50% between the bottom of the tank to being about half an inch below minimum (some pressure was released as well).

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[CastorX]

I don't really know what to do in you case, but here is what happened to me.

I bought the car in Jun 2019. It was already used, but had only 1800km in it, the dealer (DealerA) and some customers drove it for a few months. After 1 or 2 months I noticed some strange nose at startup. Like when water splashes on something or mixes with air. But I only heard it at startup for 2-3 seconds and not later. After a few such occasions I checked the coolant levels and it was below minimum when cold, and it reached minimum when it was warm. Of course the first ting was to call the dealer where I bought the car. They told me that they check all the cars before giving it to the customers and the car was also checked when they started to use it, and everything was fine. Hard to believe, but OK. I went to a dealer (DealerB) near me to let the car fill up with coolant. They told there that they did not found ANY evidence in Honda's online system that car was checked. All cars here must checked here before they are first driven on public roads (some kind of initial check or so) and it must be entered in the online system. They also told me that they couldn't even do an oil change because the car is officially not even sold to a customer. Again, according to the online system of Honda. But they filled up properly and the tech told be that they see this problem with the coolant very often because the cars are NOT properly filled up with coolant and they fave to fill them up. I told DealerA what happened and they ensured me that they checked the level at least once but probably twice and everything was fine. I think they really checked it and the coolant level was at the top but there was air in the cooling system. When I started to use the car a little bit more aggressively with 2500+km in the odometer the trapped air escaped and reached the reservoir. That happened in my case.
The short summary:
- Many cars are not properly filled from the factory
- Some cars look like they are filled but there is air in the cooling system
- If there is not too much coolant missing there is no big problem, it just must be properly filled
- If a lot of coolant is missing then it's definitively NOT good for the engine because the coolant can start to 'boil' and the engine can overheat

You wrote:
" Just went to check for any coolant leaks, still looks good. I took the radiator cap off to take a quick smell of the coolant in the tank (to know what I am smelling for) and the coolant level went from 50% between the bottom of the tank to being about half an inch below minimum (some pressure was released as well). "
I think someone should bleed and fill the cooling system in your car properly. A Honda dealer should do it just to have some record that you went there with your car and the coolant was low.

 

[Gruber]

I had a similar thing in my CR-V where the dealer replaced the coolant. Actually, I asked them why according to their receipt they used less coolant than the honda spec.
They said the spec is wrong, but it's BS, they just didn't remove all the air.
I had to add more coolant several times as it kept getting below the min line after every several days or a week of driving. Then it finally stopped and remained full.

What happens is that, as said above, if the air is not completely removed from isolated pockets, it will keep dissolving in the coolant and slowly being removed this way until it's all gone. To accelerate this process, it might help to keep opening the radiator cap (not just after driving though).

 

[CastorX]

this is false, coolant will never boil,

back to the original topic.....

it is IMPOSSIBLE to fill a brand new engine with the correct amount of coolant,

the car needs to be driven to "burp" al the air out, before you can determine the correct coolant level,

i used to work in a shop, when i did coolant changes, i would always tell the customer to drive the vehicle for a week and then come back so i can top it up for them, free of charge

Oh, OK. I heard so that it can. At around 110-120 C deg at atmospheric pressure. If there is a LOT of air in the system then even the somewhat increased pressure is not enough to keep it in liquid form simply because there is too much air in the system.
But it's not so. I learned something new today.

The dealer told me they have driven my car 1800 km before I bought it and they checked it before giving it to me. So there still was some air in the system after 1800km. Strange.

 

[CastorX]

there shouldn't be after that long

Yes, I know. So they either did not check it. Or there was a leak somewhere... but the car was checked for leaks. And i did the level did not sink since then, and I also did not hear the splashing sound since then.

 

[calonzo]

I just checked my car cold, and the coolant level is 1/2" below the MIN line, which is exactly 2" above the bottom of the tank, and I have never overheated.

If it stays at that level, I wouldn't worry about it.

 

[CastorX]

I just checked my car cold, and the coolant level is 1/2" below the MIN line, which is exactly 2" above the bottom of the tank, and I have never overheated.

If it stays at that level, I wouldn't worry about it.

I’m starting to think that almost all civics were delivered without enough coolant. Like papazz mentioned all new cars have some air in the system, but they could have at least TRY to bleed the cooling system.

 

[calonzo]

I’m starting to think that almost all civics were delivered without enough coolant. Like papazz mentioned all new cars have some air in the system, but they could have at least TRY to bleed the cooling system.

I agree. But that little bit of coolant is meaningless.

 

[fjrman]

The coolant level (cold) in the tank needs to be high enough so that the coolant outlet port near the bottom of the tank is always completely covered in coolant. This hose returns coolant to the system. Two small hoses bring coolant to the tank from the top of the radiator and the thermostat assembly. The small hoses are connected to high points to facilitate air removal from the system.

At the factory I believe they remove the air from the coolant system before introducing the coolant. This allows for quick filling of the system. Speed is critical during factory assembly.

 

[hondabandit]

My hatchback came under filled from factory. You can hear gurgling every time I turned on the AC. About a year after the purchase, I noticed the coolant level was sitting at low mark, so I filled it up and it hasn't changed since. Gurgling noise is also gone. It was such a small amount of fluid, so I just topped it off with distilled water.

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