My friends 997 4s manual is making in any gear but best heard in 3rd around 2800 rpm a rattling, buzzing, metallic noise very noticeable in cabin coming from left side rear. The noise is only under a very light load/ feathering the throttle around 2800 rpm. Putting more load or WOT, no noise
Listening outside and on bridge in neutral impossible to pinpoint location.
Also difficult to say if the noise is internal or external.
Since the noise sounds typical like a loose heat shield, cat, exhaust and to rule out the usual suspects we changed out both exhaust, cats, heat shields, drove without belt, without rear bumper, checked all coolant, AC and fuel lines etc.
Some history to this, engine was dropped to replace coolant and rear break lines, changed plugs etc.
When using PIWIS and actuate the valve lift at around 2800 RPM almost same noise can be reproduced in neutral. Changed the solenoids and did not helped.
Listening outside and on bridge in neutral impossible to pinpoint location.
Also difficult to say if the noise is internal or external.
Since the noise sounds typical like a loose heat shield, cat, exhaust and to rule out the usual suspects we changed out both exhaust, cats, heat shields, drove without belt, without rear bumper, checked all coolant, AC and fuel lines etc.
Some history to this, engine was dropped to replace coolant and rear break lines, changed plugs etc.
When using PIWIS and actuate the valve lift at around 2800 RPM almost same noise can be reproduced in neutral. Changed the solenoids and did not helped.