I took the car in at the local dealer today for a few things to be checked:
- the metallic noise originating somewhere in the accessory belt area
- the low-temperature syndrome, causing the car to run around 70ish all the time
- the turbo whistle, particularly audible when the engine is cold
The first is apparently a matter of tensioners, will be sorted for about 300 EUR. The temperature is apparently normal, these cars are supposed to run cool, according to the dealer.
Now for the fun part. They called me a few hours later and said my turbo had bent fins and they recommended replacing it for about 1100 EUR + labor!
I'm rather incredulous about that, as there's no white/grey smoke when running the car, be it cold or warm, no permanent black smoke (unless accelerating hard), no loss / consumption of oil, no visible loss of performance (but I haven't driven a 2.4 20v before, so I don't really have a base for comparison), no error lights / messages on the dashboard. I'm therefore starting to believe they're trying to make some easy money on me. The car had been taken to an independent garage a few weeks before for the same noise and they said they investigated the turbo and, while being noisier than usual, there's no reason to worry for the time being.
- are bent / deformed turbo fins supposed to generate whistling?
- what are the likely causes of the fins bending?
- what are the long-term consequences of running with bent / deformed fins? By analogy with a normal fan, I'd say it would lose balance and affect the central bearing(s), question is how long would that take.
- is there some way to diagnose bent fins apart from taking the turbo apart? I somehow have the feeling they wouldn't have had desire and/or the physical time to do that and are just trying to stick me with the worst case scenario option.
Any answer is much appreciated, as I don't know much about turbos myself. And in case anyone was wondering, even if I had to replace the turbo, I'd still buy an Alfa next time. After all, it's Garrett which is making them, not Alfa / Fiat.