Perhaps it's the pessimist in me, but I often see certain nice, desirable cars and the first thing I think of is the hidden time bomb I know lurks within.
For instance: I saw a 944S2 en route to work. First thing I thought of: "I wonder if the owner has replaced the timing chain tensioner guide ramp." If that fails, catastrophic head failure is a WHEN, not an IF.
Similarly: Volvo XC90 T6...a neighbor just bought one used and is very proud of it. I didn't have the heart to say it, but my first thought: "Hope the gearbox has already been replaced..." The GM-sourced AT in those cars is a known failure point that many XC90 T6's encounter.
A friend bought a high-mileage W124 E320 wagon that "is in really good shape, but I think it needs a tune up" because the check engine light was on and it was missing intermittently. I poked around underhood a bit, and sure enough--the engine wiring harness was disintegrating.
What other cars have these hidden time bombs that you know of?