start up noises

[Riggernut]

Good evening folks, does anyone have any clues as to why my 944T sounds like it has a supercharger on start up. The noise rises and falls with engine revs and quietens downs when warm. Only started doing since I had the belts/tensioners changed.

 

[scam75]

Difficult to not blame belt tension here although not sure why noise would diminish as engine gets warmer.

Could be an auxiliary belt too tight and not necessarily your cam belt or balance belt. Anyone never having done this job before would most probably make the balance belt too tight as it appears particularly loose when tensioned properly.

Who done the belts and did it sound like that when you picked it up?

Stuart

 

[Riggernut]

Guys at 911 sport carried out the belts, a good set of lads and the car sounded fine when I picked it up. I didn't start it for two weeks and did 400 miles in a weekend and it started occurring from then on. also quite tappety when warm although I think that's a different problem.

 

[pauljmcnulty]

Belts too tight, loosening up when they get warm? What's the difference in temperature between -9 (what we've got here at the moment) and a properly warm engine? I'd guess that the belts are shrinking more than usual in this cold.

They need to check the tension after 1000 miles anyway, so I'd watch what they do and how they use the proper tensioner.

 

[Riggernut]

Cheers Paul, makes sense. Just wanted to confirm I'd not overlooked anything else before I take it back.

 

[Lowtimer]

Mine made a similar sound after Hartech changed all the belts in March.. Quite an interesting supercharger-like whine It gradually faded quite a bit as I got towards the re-tensioning, which I had them do around 1400 miles after installation. When they re-tensioned it, it was just a little louder again for a couple of hundred miles but then faded slowly again.