Coolant light: just add more liquid, or is definitely worse?

[kayger12]

Keith, you're getting at the issue I was alluding to in my original post. If its supposed to be a closed system, is it ever "really, truly, actually OK" to need to top off with a cup or two of coolant? Or is just "not that big a problem"? To have a dealer do the pump/thermostat/housing trifecta, what would you expect all in? What about at an indy?

My understanding is that you should never have to top off the coolant unless there is a leak somewhere.

I agree with Dalton that your light was triggered by coolant flowing into the core when you turned on the heat, but the fact remains that the air pocket in the core had to come from somewhere.

I wouldn't be overly concerned about having to replace some coolant here or there, but I would want to find the source of the gradual loss.

Little problems aren't a big deal, but left unresolved (especially with the M54 cooling system) they can turn into big problems.

I would top off and keep an eye on it. I would prioritize replacing your water pump and thermostat within the next 5k.

Above 60k with an original water pump you're on borrowed time, imo.

Bruce's suggestion about the expansion tank cap is a good one as well. And cheap/easy.



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[2004_blue_zhp]

Radiator cap = Expansion Tank cap or is different?

[BCS_ZHP]

It's the same, only one cap in the entire cooling system, and the only place you can add coolant too.

[kayger12]

Radiator cap = Expansion Tank cap or is different?

Sorry. Meant expansion tank cap. Fixed.

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[CERF04ZHP]

I had the same problem a couple years ago... I would turn my heat on and the light would come on. Turn the heat off, light off. Also coincidentally, the heat was very inconsistent, as in when I had it on 75 or warmer with the fine tune adjustment wheel turned all the way hot, the heat coming into the cabin was luke warm, sometimes cold and rarely hot. Dane suggested I had a problem with my heater core valve: http://www.ecstuning.com/BMW-E46-330...alve/ES177235/
Purchased, replaced in about 30 minutes, topped off and bled coolant system, problem solved.

[2004_blue_zhp]

Last question: Everyone has emphasized that you shouldn't open the expansion tank cap when the engine is "hot". Ok, makes sense. I'm i Manhattan in NYC, so my car lives in a garage. When I go get it, the guys need to bring it around, so I have no idea how long they ran the engine and how long it's been sitting still before I get there. I'll need to pull it around the block to put in the coolant. (They are very strict about "no work being done on premises".) What is "cool enough" to open the expansion tank? Engine temp in the blue on the dash? Everything in engine compartment cool to the touch? A certain number of minutes after turning off the ignition? Thanks for your help.

[BCS_ZHP]

Grab the upper radiator hose, it feeds into the expansion tank, if you can squeeze it then the coolant is still cool enough to open the expansion tank. It the hose is too hot to hold and/or you can't squeeze it, don't open that expansion tank until it cools down some.

[nike001]

My understanding is that you should never have to top off the coolant unless there is a leak somewhere.

Not necessarily true. The cooling system is a closed system, but it's not unlikely to top it off every now and then. It's actually a ritual that most techs do at the BMW dealer I work with. When buttoning the car up, they had windshield washer fluid and top off the coolant.

[kayger12]

Not necessarily true. The cooling system is a closed system, but it's not unlikely to top it off every now and then. It's actually a ritual that most techs do at the BMW dealer I work with. When buttoning the car up, they had windshield washer fluid and top off the coolant.

If you have to top it off, it's because you're losing coolant somewhere.

It's a closed, pressurized system. If you don't have a leak, you should not need to top it off.

Are you saying a properly operating system "uses" coolant?

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[2004_blue_zhp]

Ok. Finally got around to topping off the coolant. I added about 1.25 liters of fluid. That got the lower sphere on the floating stick up to the top of where the expansion cap screws on. I.e. "max fill". What do you guys think. Is adding that much coolant cause for concern? For example, does anyone know how much coolant is the difference between "min fill" and "max fill"?

(Brief aside: I added about 0.75 liters of coolant and about 0.5 liters of distilled water. I was alternating one and the other and ended with coolant so wound up with a bit more concentrated than 50:50. I figured it didn't matter given that the whole system is more than 8 liters. No issue with that logic, right?)