This is for any owners who enjoy doing their own servicing. Just flushed my cooling system after 2 years and 15000 miles. Radiator has a drain plug on the passenger side but that doesn't drain the block or oil cooler. I removed the radiator hoses at the engine and the hoses at the oil cooler. Ran water through all these openings until the system was clear. Used compressed air at the filler cap to get all the water out of the engine block. REFILLING......the most critical step of the procedure is here. You must open the bleeder valve during refilling. It's located under the black triangular panel that surrounds the filler cap (upper LH corner of engine compartment). Without this valve the system would be full of air. Have the valve open as you refill and the air vents through the cap opening. NAPA auto parts sells ZEREX G40 coolant (bright pink) which is the formula specified by Porsche, $20 gallon. Get distilled water, mix 2 gallons of 50/50 and refill. Takes the entire 2 gallons if you drain everything. Good luck ! Great feeling knowing my cooling system is pristine again !

 

I'm surprised you didn't use any social tools like the coolant vacuum filler kit.