Water pump failure (intermittent, therefore difficult to diagnose)
Serious overheating as a result of both head gaskets blowing. One of the top cylinder blocks cracked too.
Faulty wiring caused short a circuit and one of the spark plug coils melted and cause a fire.
Gearbox has started to "catch" when changing from 2nd to 3rd gear.
In fairness to the 156 it does have some good points. In my opinion this car looks great, sounds great, and when it works it's an absolute pleasure to drive. It delivers real power. It handles beautifully. It is comfortable, and you do get noticed by other motorists and pedestrians.
The feel of the build quality isn't that great. Doors just don't shut like they do in German cars. You might have to slam them a second time just to make sure. The interior is very aesthetically pleasing, but the quality is sub-standard. Just compare the glovebox on the 156 to that of an older Audi A4 for instance.
The major problem is the dismal reliability, the phenomenal maintenance costs, and of course the depreciation. How can one justify owning and maintaining such a vehicle? And even then, what fun is it to own such a car when it spends so much time in the garage.
Maintaining a 2.5 V6 is also not straightforward. The car is designed so that servicing is difficult, and if you look outside the main dealers and Alfa specialist centres, many mechanics won't touch it, and it became apparent to me why. Changing the oil filter is incredibly difficult to do as it's very difficult to reach. Even changing the spark plugs requires disassembling part of the engine and is a job that will take a good 3 hours.
Go and get one if you like, they depreciate so fast that you'll probably be able to pick up a high mileage 1999 car for £3000. Incidentally that's the same cost for replacing two cylinder heads if you order the parts from an Alfa dealer. And that doesn't include labour.
Fuel consumption on the 2.5 V6 engine is also high, but that's to be expected on a performance car so I can't complain there.
I intend never to purchase another Alfa Romeo again. It's a painfully expensive experience, especially if you end up with a bad one like I did.
To summarise my expenditures, I bought the car in 2003 for £6500 second-hand. In just over a year I've spent at least £4000 on the car. That's money I could have spent on so many other things, so I'm getting rid of mine. Just in time too as the gearbox is beginning to fail - and I don't even want to know what a new or reconditioned one will cost.
I advise against buying one. If you're after something sporty, then there are so many other good looking and reliable cars out there. If you want to start a love affair with the beautiful Alfa's, just watch out. You will get burned, and your wallet will be sucked dry.