The mechanic i use on occasion when i feel something is over my head was a BMW tech for 15 years. I asked him about the coolant level because i have had the same issue a couple of times; he told me it is the only vehicle he has ever seen that will occasionally have coolant disappear whether it evaporates or whatever. he checked mine out for leaks and the whole cooling system was fine.

Alternator
 

I had the coolant warning a few weeks ago and we replaced the hoses at the water pump. A week later the warning is back. This morning I filled it up and started a 70 mile trip and the light came on again 10 miles into it.

I took it to my BMW dude and saw the damn alternator leaking after he pressure tested it. We replace it tomorrow. My saving grace is a chick who works for a parts house and got the Bosch unit for $277 (her cost).

Coolant doesn't just disappear, so it sounds like it's time for the same suggestion I've given people on here and my customers...with your mileage, it's getting close for a complete cooling system overhaul. It's hard to swallow, but considering the aggravation of being stuck on the side of the highway, towing charges, [potential engine damage, etc in the end it's easier to just spend a weekend replacing everything and forget about it.

Prestone will work fine as 50:50 ?! Thanks

No Prestone, you can only use BMW or Zerex G05 mixed with distilled water.

thanks , i end up just adding some water. It was empty

Distilled bottled water only I hope. Tap water has too many deposits which can cause clogging issues down the road.

:confused::confused::confused: i hope so. i guess mechanic should have known and did it right way with Distilled water. if not he might have a problem:dunno:

Ehh, I've seen some do it and some don't. I've rebuilt heater diverter valves that had stopped working, but some were so far deteriorated that there was simply no saving them. The image below wouldn't have happened with the proper coolant, distilled water and regular changes.

:wow::wow::wow: wow what a mess !!!! Learned my lesson, first thing in the morning will ask him what did he use

Thanks