Porsche can look perfect and still hide big problems. Time to find them is before you buy it. 13 years every day on these cars, I learned where they hide. Inspection should be done by somebody who works for you, not for the seller, and you pay for it.
First the computer. I connect the diagnostic tool and read fault memory of every module, not only engine. Airbag computer stores crash data. Signs that battery was disconnected or faults were cleared just before the sale, this is a warning. I divide miles by engine hours, and fuel trims and misfire counters tell a lot too. Open recalls, campaigns and warranty extensions get checked by VIN, Porsche runs them by VIN, not by model year.
Then over-rev report. It counts ignitions in each rpm range from rev limiter up, and saves engine hours of the last over-rev in each range. I wrote separate post how to read it.
Then engine. Compression and leak-down on every cylinder. On engines that get bore scoring, I scope the cylinders, from below too. On 2014 to 2016 991 or 981, one coil comes out. Porsche found coils with bad diode that can hurt cylinder walls, and fixed ones are marked NEW. Air oil separator gets manometer test, and closing the throttle sharp from high rpm shows smoke from guides, seals or AOS. Leaks at rear main seal and IMS cover, and rear main seal you can fully judge only with transmission out. On Mezger cars, coolant pipes. This is the 996 and 997.1 Turbo, and every 996 and 997 GT2 and GT3, including 997.2 GT3, GT3 RS, RS 4.0 and GT2 RS. Pipes are glued in, and when one lets go, coolant is gone fast. I want to see proof they were pinned.
Car should arrive cold and be started cold. Warm engine simply hides things. Then some checks count only hot: cam timing live data, oil level on dry sump GT cars, and manometer.
Some things are model specific. On 4.0 GT engines rattle near the oil pump is normal. Porsche has sound file for it, and says engine replacement for this noise is not authorized. Rattle that does not match the file is real finding. On 992 with PDK, judder together with low PDK oil and overfilled gear set means internal leak, and Porsche replaces the transmission. PDK oil pan gets blamed for leaks it doesn't have. The 991.1 GT3 has its own list, I wrote about it separate.
On Cayenne, Macan or Panamera the list changes. Coolant pipes: plastic ones under the intake on 4.5 V8, glued ones at thermostat housing and rear crossover on 4.8. Camshaft adjuster bolt recall on 2011 Cayenne S and Turbo and 2010 to 2012 Panamera V8. Shifter cable bushing recall on 2003 to 2010 Cayenne and 2010 to 2016 Panamera, lever shows Park and car is not in Park. For 958 transfer case Porsche has a factory test for the jerk in tight turns. On 2014 to 2018 Macan transfer case extension ran out, and timing cover leak can be two screws, not engine-out job. Some extensions are still running, like PCV hose on 2019 and later Cayenne V8 for 15 years. They can be checked by VIN.
Then rest of the car. Every warning light has to come on with the key. Paint thickness and hidden welds for accident repair. Suspension, brakes, brake fluid, tire age. On centerlock cars wheel comes off, to look at drive pegs. Service history. And drive long enough to get everything hot, with live data running.
Air-cooled cars get different inspection, I wrote separate post about that.
You get written report with photos and borescope pictures. I inspect cars here in Colorado for buyers from other states too. Let's say you buy from far away, be on the phone that day. When I find something serious, I call you before I go further.
Almost every car has something. Some cars I tell buyer to walk away. Either way, you know what you buy and what it will need.
Also: Porsche service · Over-rev report · Bore scoring · IMS bearing · Air-cooled 911 PPI · 991.1 GT3