celticdude69

My 07 TSX is one year old with 16K miles. Coolant level has already gone down from MAX to MIN level. Is this normal? I've had hondas which have never lost that much coolant in a year.

BTW, I live in SF bay area.

Simba91102

I would say no. I assume you're sure that it was full (at the MAX line) when it was new. I found mine (an 05) to be low some time last year, and since I could find no trace of where it might have gone, I suspect the dealer didn't completely fill it when the coolant was changed. That's the only time I've found it to be low (3 yrs old, 70K miles)(the car I mean).

zguy95135

Check to see that this isn't happening.
https://acurazine.com/forums/showthread.php?t=42288

slickrab

I believe that is normal. I also have an 07' and when the engine is warmed up it will be at the max level. When cold it will be on min. If you ask me why, I wouldn't know how to answere that. Just don't fill it to the max level whn cold b/c it will than leak droplets all over the engine bay.

Simba91102

I'd like to hear from others here, but I will gently disagree. The resevoir on my 05 it seems is on the max line at all times.

LukeaTron

This is how it's supposed to work. The engine heats up and coolant goes with it. Things get bigger when they're warm so the fluid expands. The volume of fluid the engine, radiator and hoses can hold is a fixed amount so now not all the fluid can fit in the system. Enter the reservoir. The reservoir is just a temporary container to hold the difference in fluid volume from cold to hot.

When the engine gets hot, the reservoir fills up. When it cools back down, the shrinking fluid gets sucked back into the engine (this makes me think of the shrinkage episode of Seinfeld). If you didn't have the reservoir, the fluid would just spill out on the road, then when your car cooled down, it would suck air back in. Air in the coolant is best avoided.

Celticdude, as long as it's over the low line, you don't have anything to worry about. If you top it off when the engine is cold, some fluid will just get pushed out of the reservoir when the engine heats up and when it cools down, the level will be right back to where it started.

poltergeist

Absolutely correct. Also note that because the recovery tank is not sealed, and since the coolant is around 50% water, there's a certain amount of evaporation out of the tank over time.

celticdude69

Thanks LukeaTron, that's very helpful info. I'll check the levels when the engine's hot and cold and compare.
Slickrab, thanks for the advice, too.

CarbonGray Earl

+1

I have an 05 as well (auto).

rx280

I can provide a conclusive report re. how the coolant level in the reservoir (overflow tank) changes as the engine warms up and cools down.
I had my ’04’s coolant changed at the dealership (along with the MT fluid and brake fluid) late last year. I’m one of those people who checks things under the hood every week or two, and, before the coolant was changed, the level in the reservoir was essentially constant from check to check, with the engine cold. The coolant was probably about 2 inches below the MAX line week after week, month after month.
A couple of days after the fluid changes were done, I opened the hood to check the fluid levels and was shocked to find that the coolant reservoir was empty. Needless to say, I returned to the dealership ASAP. They added coolant to the MAX line and sent me on my way.
Twenty-four hours later the coolant level was below the MIN line. Back to the dealer. This time they declared that there must be some air in the system. After about a one-hour wait, I was assured that the air problem had been taken care of. As I recall, I had to go back one more time just to have the coolant topped off, but since then, no problems, and constancy has returned.
When the engine is warm, the coolant level is right on the MAX line. When it’s cold, the level is about half an inch below the MAX line. (Maybe it’s three-quarters of an inch, but absolutely no more than that; I’m trying to avoid going outside to take a precise measurement.) Bottom line: From my experience, the notion that the coolant level moves way up and down as the engine heats up and cools down is incorrect.

rx280

For the sake of maximum accuracy, I just went out and measured how far below the MAX line the coolant is when the engine is cold. (It's at the MAX line when the engine is warm.) The estimate I gave in my previous post -- half to three-quarters of an inch -- was a little high. The actual figure is just three-eighths of an inch.
So, again, in my experience, at least, the difference between the cold and warm levels is pretty small.

celticdude69

So, based on what you say, I guess it's safe to top off the coolant up to the MAX level when engine is cold. This won't result to coolant overflow when the engine gets hot, being that there's at least a couple of inches from the MAX level to the top of the reservoir. I just checked the manual and it says to top off up to the MAX level.

LukeaTron

Even if it does overflow, it's not a big deal. It just drains out the overflow hose onto the ground.