Hi everyone,
Long shot but someone here might be able to help. Have a 1999 SL600 with the M120 engine. Engine is absolutely as smooth as silk apart from one problem...when you start it from cold there is a slight rough noise to the engine....which gets louder with engine speed and then as you go through 3000rpm it disappears completely....let the revs drop back below 3000rpm and click...there it is again. Its definitely not directly coming from directly the block but an ancillary. Its almost like a valve snapping shut at 3000rpm and cutting the noise or a clutch of some sort. Id even go as far as to say that there is a little rush of air almost like a blow off valve noise as you pass 3000rpm and the noise disappears.
Sorry I cant be more specific! No codes, no errors and like I say the engine is absolutely silken smooth and silent when up to temperature. Perhaps its is part of the secondary air injection system and it might be perfectly normal.
Cheers in advance to any pointers!
Long shot but someone here might be able to help. Have a 1999 SL600 with the M120 engine. Engine is absolutely as smooth as silk apart from one problem...when you start it from cold there is a slight rough noise to the engine....which gets louder with engine speed and then as you go through 3000rpm it disappears completely....let the revs drop back below 3000rpm and click...there it is again. Its definitely not directly coming from directly the block but an ancillary. Its almost like a valve snapping shut at 3000rpm and cutting the noise or a clutch of some sort. Id even go as far as to say that there is a little rush of air almost like a blow off valve noise as you pass 3000rpm and the noise disappears.
Sorry I cant be more specific! No codes, no errors and like I say the engine is absolutely silken smooth and silent when up to temperature. Perhaps its is part of the secondary air injection system and it might be perfectly normal.
Cheers in advance to any pointers!
