[Denny347]

I just topped off the coolant reservoir today. I noticed the top of the level indicator was even with the top of the filler threads so it needed a bit of topping off. I added MAYBE 6oz before the level indicator popped up to show full. Last time I did this was about 6 months ago. No white smoke when I drive or the smell of antifreeze in exhaust and I am not leaking it anywhere I can see. Is this normal and where the hell is it going?

[Efthreeoh]

Replace the reservoir cap. The pressure relief value weakens over time and lets coolant in the form of vapor escape the system. My high mileage car was doing the same thing. I replaced the cap and it solved the issue.

[BashShah]

This suggestion is a shot in the dark....most like won't help....
And the poster response above is most like right.

But did you ever have the coolant changed?
For any reason.
Did they properly purge the air and ran the pump for 12 min?

Look up coolant drain DIY.
The last steps, making you water pump run for 12 min to drain the air.

DN

[Efthreeoh]

The once the engine is run, or the pump is run, the system purges air from the cylinder head water jackets (the only place air can be trapped). The need to add 6 ounces to a E90 cooling system is perfectly normal.

[AdamN52]

I've had to top up once or twice in the past two years - a few ounces total maybe? Nothing to be worried about unless it's often/large volumes.

[Denny347]

I'm at 90k on the clock so changing the cap would be a good idea. I'm likely due to replace the coolant. Its on my list. Might actually do it myself.

[GoRomeo]

OP, adding a bit of coolant is Normal. I have a quart of coolant in my garage just in case I need to add. I believe i add a cup coolant every year or so...

[Raman335i]

Is there a specific coolant to use?

[GoRomeo]

Originally Posted by Raman335i

Is there a specific coolant to use?

yes, the one at the dealership. Nothing else.

Adding distilled water works as well.

[blackturbo]

Originally Posted by FCobra94

Adding distilled water works as well.

I agree if its a minor top off.

pentofrost nf is actually oem coolant in concentrate form as well.