markusius

I forgot to add to my previous post that this forum link discusses a very similar noise:

https://rennlist.com/forums/996-foru...-on-99-c4.html

nzporsche944s2

+1 on the engine mounts making the harmonic buzz
My 1990 S2 started doing it immediately after changing the engine mounts with aftermarket ones. It happens to me intermittently but at a lower rpm range than yours (mine is around 900-1200rpm) but sometimes not at all. Occassionally when coasting to a stop it will buzz through that range and stay buzzing at idle but a light blip on the throttle and it goes away.
Mine is definitely the engine mounts I just haven't got around to changing and I'm learning to live with it...

tomv944

My 90 S2 Cab had a similiar Hum at about the same speed after I had the water pump, timing belt cam tensioners done by my local mechanic. I took it back and they tod me the either the cam tensioners or the balance belt was just a bit too tight they readjusted it and the hum is gone. Sorry I can't be more specific as I did not do the work myself.

mikey_audiogeek

The original problem in the first post sounds to me like power steer hose "hum", relatively common on the S2 and 968. All symptoms line up. Caused by some weird interaction between the PS relief valve, hose lengths and/or low fluid level.