Finally, the "cause" of engine noise at cold start up explained
10-17-2007, 07:22 AM
#16
I also have smoke on start-up, sometimes less, sometimes more. There is also a half-second drill-bit-in-concrete sound on start up, probably because oil is missing somewhere. Both things differ, however, depending on whether the car has been standing for one day, or two days.
There are lots of other sounds as well. The gearbox whine when idling along, the clutch bearing or gears with clutch engaged in neutral, the vibration from the inside rear-view mirror housing when the temperature and humidity is just right, the vibration from the driver´s side door opener, rumbling of brakes at a certain temperature...
In my mind, all part of the whole experience.
There are lots of other sounds as well. The gearbox whine when idling along, the clutch bearing or gears with clutch engaged in neutral, the vibration from the inside rear-view mirror housing when the temperature and humidity is just right, the vibration from the driver´s side door opener, rumbling of brakes at a certain temperature...
In my mind, all part of the whole experience.
10-17-2007, 09:35 AM
#18
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the turbos with the same block don't have the noise - I really doubt piston slap. It may be more valvetrain related or flywheel from the starter motor. Mine only did it for a couple of seconds max. It seemed to me like some kind of valve was open and then as soon as some vacuum built up the valve closed and the noise was gone.
Actually, I remember when I did euro delivery the noise was constant when my CEL came on - it was a disconnected variable cam timing switch. It has to be something valvetrain related!!
Actually, I remember when I did euro delivery the noise was constant when my CEL came on - it was a disconnected variable cam timing switch. It has to be something valvetrain related!!
10-18-2007, 05:11 PM
#21
What you are hearing at cold start up is virtually guaranteed not piston slap but rather the noise the exhaust makes due to extra air being pumped in the cats for quick warm up. You will note that after usually about 1 min it magically disappears. This is to also be contrasted with the rattle you hear only for a few seconds on start up after the car has been sitting a few days but usually never hear if driven every day which is presumably a function of oil drainage over the course of a couple of days.
