[Hoooper]

Ok, so who all has had the low coolant warning? I just got the light, and my first thought of course was that I had cracked my EGR cooler. I don't see any steam on start up though. After a quick search it looks like low coolant is a fairly common occurrence on 335s, particular as weather starts to turn colder. Considering this is the first time anything has been added at least since the "free" maintenance period ended and possibly ever over 95k miles, that's not too bad, but has anyone else had to top off their coolant?

On a side note, it would be real nice if BMW would label the reservoirs a little better. The coolant reservoir says nothing about being coolant, at least not in English. You really shouldn't have to follow radiator hoses to figure out which reservoir is the right one, or figure it out based on process of elimination (coolant is not for a windshield and ATF wouldn't go well in it).

[modobrew]

I had to top mine off a while back. I just hit it with a little bit of distilled water and called it a day. Warning went away the next day.

[WreckerX5d]

A little bit ago I topped mine off, it was at the minimum mark. I got a free radiator replacement almost a year ago as well.

[kbsilver]

While the cooling systems are 'sealed', there is still minor loss over the year. When the colder season arrives, this is typically when the low coolant sensor will trip. Having to add a cup or so per year is perfectly normal. NOTE: It is best to fill to the MIN level. Filling to the MAX will only result in burping out some coolant during high temperature operation, plus puts added pressure/stress on all those plastic cooling components (less room for expansion).

[Roadrunner143]

I got the warning once in the last 70,000km of ownership (got the car at 75,000km, currently at 145,000km). Passed by the nearest BMW dealer when it happened, they topped it up for free. It was "missing" some 1/2 liter approx. But I think they went to the max line, not sure. Never had issues since then.

Like kbsilver said, it is a sealed system but this is real life... ninjas get in there once in a while and steal some...

[TDIwyse]

You weren't doing some aggressive accelerations when this happened, were you?

I've had that warning go off a couple times whilst at the dragstrip. The aggressive launches seems to shift the fluid enough to trigger it. I've checked the level each time after the warning (at home after the engine cools) and it's never been low.

[Hoooper]

The light first went off after a cold start on a hillside parking lot. Then it went off again next time on a relatively flat parking spot. I checked it cold and it was definitely low. I will be checking it again in a few days just to make sure nothing is going on but it sounds like this is normal. I guess with the black bottle I just dont notice it until its low vs a normal bottle where I add a tiny amount at a time.

[Luckystrike24]

I've had mine come on twice and filled it twice in the span of a year and half. I'm going to put some dye in the coolant and wait a little while and see if I find dye to show up anywhere. I'll let you know if i come across anything. I've seen some people complain the pump has a small crack in the housing. I'm not too worried about it personally, but def. want track it down to see if there's a leak anywhere.

[BB_cuda]

My car only has 34k miles. Unsure if it is miles or merely time that would get you down a 1/2 L. I had my coolant changed per Mike Miller maintenance (every 2 years) and I'm about 1 yr behind for that schedule. I had car at Indy mechanic for brake fluid flush and had the new jug of coolant in garage. So, I added that to his list to get it done. He explained that he has machine to evacuate the system and add coolant back in such that no air pockets in system. He says this is first BMW diesel he has ever worked on. He does plenty BMW gassers though.

EDIT: he filled to max line with a 50/50 mix from my concentrate BMW brand coolant