a) External coolant leak
b) Internal oil/coolant intermix
c) External Oil leak

~ 3/8" drive ratchet, with 3" and 8" long extensions, 13mm & 10mm short socket, 8mm Hex drive, T30 and T25 Torx drivers, wobbly extension
~ 1/4 drive ratchet, with wobbly extension, 8mm long socket
~ Long flathead prybar, flathead screwdriver(long and short)
~ Long needle-nosed pliers, with 90-degree bent tips
~ Large capacity drain pans: 10qt for oil, 2 gallons for coolant
~ Adequate portable lighting
~ Hydrometer
~ Oil filter tool

~ OEM equivalent oil filter and o-ring (Mahle, Hengst, Mann-Filter)
~ 2 Gallons Porsche or VW G12 coolant, 2 gallons Distilled Water
~ Nine US quarts of 0W-40 motor oil (Mobil1, Castrol, Motul, Red Line, Shell Rotella T6)
~ Replacement oil cooler (Behr/Hella #948.107.276.03, Nissens #90375)
~ OEM Porsche oil cooler seals x2 #948.107.175.00
~ High-temperature Heavy Grease

~ Raise Turbo to Special Terrain Level - set suspension to "Regulation Switched Off."Non-Turbo needs to be raised on ramps or jackstands.
~ Remove all belly pans, lower air deflectors, including transmission cover(10mm, T25)
~ Remove lower subframe cross bar, forward of oil cooler(T30, 13mm)
~ Drain coolant from reservoir, with Hydrometer. Spray heavy degreaser in tank to dislodge trapped oil. Top off with distilled water, for subsequent flushing
~ Finish draining coolant from either coolant petcock(2003-2005) or disconnect lower radiator hose, at radiator(flathead driver, to unlock Henn Coupler clip)
~ Drain all oil from upper and lower drain ports. Vehicle MUST be completely level

~ Raise factory oil cooler spring clamps(coolant side) to clear coolant hose joint flare. Passenger side is easy. Driver side has only less than 4" clearance to fan shroud. The spring clamp rests below oil return line(Turbo). Use long needle-nosed pliers, with curved tips to bring clamp up to the high part of the hose(second hand necessary):
~ Place drain pan or shallow baking sheet below oil cooler to capture coolant first. Do this by pulling both hoses off now. Do one hose at a time. Expect to see 1/2 gallon of coolant pour out
~ Remove the four T30 bolts holding the oil cooler to adapter bracket. Keep another drain pan ready below. Oil will seep, once the bolts become loose. One quart of oil will gush out, once the bolts are off. A second set of hands greatly helps, here
~ Remove oil filter(oil filter tool)
~ Remove and dispose of spring clamps, they suck
~ Clean up oil cooler mounting adapter bracket and oil filter housing boss

~ Place new screw-in band type hose clamps exactly as follows:
Passenger side clamp rests on top of cooler adapter bracket, with worm screw portion facing OUTWARDS towards passenger front wheel. Screw faces directly forward. Coolant hose threads through loosened clamp.
Driver side clamp rests on top of cooler adapter bracket, with worm screw portion facing OUTWARDS towards driver front wheel... but below Turbo oil return line. Screw must always face directly forward. Coolant hose threads through loosened clamp. Due to nearly zero visibility of this clamp - a second hand must keep clamp screw facing forward, by feel alone!
~ Prepare cooler oil seals by applying liberal amount of grease to adapter bracket oil openings. Pay close attention to orientation of oil seal rubber nubs. They only go in one-way. The grease should hold the seals up in place
~ Pre-Install new oil cooler by lubing the oil cooler hose necks with coolant. Then start the hoses in, meeting the pipe connection necks first. Torque all four oil cooler mounts to adapter bracket(T30). Using curved, long needle-nosed pliers - gently pinch each hose at the soft portion as you pull-down hoses to mate the oil cooler body, on both sides.
~ Now tighten hose clamps, making sure the screw heads face forward, at all times. Passenger side is easy. Driver side requires patience and lots of cursing. Use second hand to keep worm screw head always facing forward. Due to the design of the oil cooler adapter mounting bracket - the band clamp on driver side must not shift... or else a telescoping magnet needs to bring screw head and correct clamp orientation back into position. This is arguably the most difficult part of the entire job
~ Install new oil filter and torque(oil filter wrench)
~ Re-torque coolant drain petcock or reconnect lower radiator hose connection. If the latter - test by making sure lower hose connection cannot pull itsef apart
~ Install lower subframe cross bar and four Torx bolts to lower front valance(13mm, T30)

~ Refill pre-mixed, fresh coolant back into system. Minimize trapped air, by pouring coolant very slowly, almost a drizzle until level reaches MAX mark of reservoir. Leave coolant cap off
~ Refill 8 quarts of fresh 0W-40 oil initially
~ Start vehicle and run heater on HIGH. Top-off coolant as needed
~ Check oil level to make sure oil cooler accounted for oil capacity reached. Most likely oil cooler will require an additional 1/2 quart of oil
~ Leave belly pans OFF and monitor for external leaks for the next 24 hours. Top-off all fluids, as necessary. Belly pan install is reverse of removal