You can borrow from a car parts store. (advance Auto for example). You buy it but return for full credit.

I developed a hairline crack in my client reservoir. Coolant is florescent, you can use a UV flashlight to help find leaks. I was about to get the pressure tester when I found the leak on the side of the reservoir.

The stiffening plate on the bottom can catch a month of drips before any will come out on the driveway so if the leak doesn't jump out at you, you may have to remove the plate to see. (just make sure to replace the four aft bolts since they also hold the sway bar before you drive.

Common source for a slow leak is either the reservoir or one of the o-ring seals going in or out of it.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)