@Xulfiqar I recently visited Afzal (Abdul Hameed & Sons) for some suspension work on my 2009 Corolla diesel. During the test drive he mentioned that the engine noise didn't sound right and that I should get it checked out. He revved the engine and said that in high revs engine sound "thora phat ke aa raha hai". Now I don't know the level of Afzal's expertise with diesel engines but this is something I had also suspected for some time but hadn't had it checked out, mainly due to the fact that I don't know of a good, reliable diesel mechanic in Karachi. The car has not to date required any major mechanical work (the suspension job mentioned above being the first non-denting/painting and non-routine maintenance work the car has gone if for) and the last thing I want is some anaari mechanic who doesn't know diesel engines to have a go at it.
So my first question is - what could be the probable cause of the engine sounding like described above. It definitely sounds a lot heavier, a lot louder than when the car was new. I just put it down to age and normal wear and tear. Could it be something else? Afzal mentioned something about a "jaali" which can sometimes tear. I'm still getting a decent average (between 13-14 km/l) and there is no noticeable black smoke.
Second - are you aware of a diesel mechanic in Karachi who you are able to recommend?
