The head gaskets failed in the car's seventh year on the road. A biggie.
The transmission fluid reservoir sprang a drastic leak.
Unless the tires are really good, the rear end can fishtail on wet or snowy pavement.
The air conditioner. What air conditioner? It didn't work from the time I got the car and I never bothered to get it fixed. That's why there are these scary little fans you can buy and plug into the cigarette lighter outlet. Watch out though. Those little things are seriously wonky.
I purchased a used 1994 Mercury Sable wagon in 2000. It already had 150,000 kilometers on the odometer and I got it for $4,000. Basically I got what I paid for and was not surprised or upset when the head gaskets blew after a year. Apparently, the head gaskets in Fords are impossible to service until the entire engine has been removed and the process is expensive. It only cost a little more to replace the engine with a ($2,000 total) rebuilt one, so we had a Windstar engine installed. The 1998 engine has been like a dream ever since. No problems at all.
Other things have gone wrong occasionally, but nothing more than we expected. The driver's side door handle broke, the rear wiper motor failed, the blower motor had to be replaced, and once in a while a wire or hose had to be replaced. My mechanic puts in used-but-still-good ones for me for free.
The next biggest repair should have been rebuilding the transmission because I lost all the transmission fluid on a short drive. Luckily not far from my mechanic's establishment. I had no idea what was going on with the car, but took no chances and drove straight there. Whew! No damage was found with the transmission and the reservoir or whatever was replaced.
Basically, the key to keeping an old car on the road is regular maintenance and frequent oil changes. I'm at 215,000 kilometers and don't see why my Sable Wagon can't go over 400,000 like my brother's Crown Victoria has done. It is still on the road and going strong.
We never buy new vehicles. Just as many things can go wrong with new cars as used ones, and we don't have the stress and frustration of arguing with dealers about warranties not being honored. Since a new car devalues by half just driving it off the dealer's lot, we find ourselves ahead of the game by buying used cars, even if something major happens. The biggest stress is simply in dealing with sales people. It is to be (sadly) expected that used car dealers will lie and scam to make a sale. We just pretend we are girding ourselves for battle and steel ourselves against their tactics. Sometimes the salesmen get confused and think they are selling real estate. "We've got another interested buyer. You better act fast." (Snicker).
We do our research and get the best used car we can for our money. Sable Wagons have almost as good a reputation for crash worthiness as Windstars.
The rear seat folds down to provide a huge cargo area. I've carried lumber, rocks, bricks, furniture and bags of cement without damaging the suspension. It is an excellent work horse and is comfortable on long drives. The engine runs quietly and smoothly, and has plenty of power, even with heavy cargo, to pass and merge on the highway. Until I replaced the old tires with good snows, the rear end 'traveled' a bit on wet pavement. Fishtailing can happen with tread wear. These cars really do need good snows. All-weather tires are no good for winter driving here in Toronto. Naturally, I take it easy during wet or snowy conditions, but feel safer with the new Goodyear snows. I'll probably get Toyo all-weather tires for summer.
I guess it all comes down to attitude and expectation. We consider vehicles to be tools and expect these tools to cost about $3,000 per year (including cost of car, repairs and gas). If everything goes well, we sometimes get a bonus year or two with only maintenance and gas as expenses once the car is 'paid for'. In all, I'm very happy with my 1994 Mercury Sable (with a 1998 Windstar engine). A bit of rust has shown up on the tailgate and a few blisters here and there, but I never bothered to get it rust-proofed. Oops! I don't mind paying for maintenance and other repairs, so unless the engine blows again I'm happy with what I've got.