Mystery Coolant Leak
2003 R53 140,000 miles
Coolant "dumps" out over the head shield for the headers. Splash pattern indicates that it's coming from somewhere around the reservoir. It already has an aluminum aftermarket reservoir. I pulled the reservoir completely out. No cracks in the tank, and the inlet and outlet hoses are perfect. Replaced it, filled it with coolant, watched it get up to temp, reved the engine to get it hot, no leaks at all. Left for an hour and noticed a small puddle of coolant under the tank on the heat shield.
Now when the first leak happened on the way back from work, I would say that it dumped out vs leaked. I was able to park the car within 60 seconds and the reservoir was empty.
I figured, since the aftermarket tank doesn't come with a cap that the original owner just used the same cap. So the cap would be from 2003 and may have failed. To me this seemed like the only option. No leaks anywhere in the area, so the only option would be the old cap has failed and can't support the pressure anymore. Not the case. Purchased new cap. This morning the same thing happened, except on a lesser scale.
No chocolate milk either, so it's not leaking in the oil.
Someone please enlighten me. I'm going nuts over this.