I have a constant whine...

...and no, its not coming from the passenger seat! Hi guys, been a lurker here for a few months now having picked up a '99 C4 Cab at the end of September. Keep meaning to start a thread on it, I'm sure I'll get to it one day. Anyway, after some advice if I may - I have a whine. It was apparent when I purchased the car but it wasn't too disturbing and had a PPI at a specialist who gave it the green light so didn't suspect it to be anything to worry about. Anyway, the more I drive the car the more apparent the whine is, to the point where I think it may even be getting louder/higher pitched at times. First thing I did was replace the belt and have recently replaced the bearings in the tensioner & idlers. A friend suggested I run the car without the belt on idle to see if the whine is there and it is so this rules out any of the other pulleys on the belt system presumably? In my Internet hunt for answers I came across a thread on PH with videos of what sounds exactly like the whine I'm getting. The car had recently rebuilt at Hartech and there are a fair few comments from people saying 'thats normal' including from Hartech themselves but Im not convinced that is the case, certainly for mine. As I say, the whine appears to be getting worse and is very audible in most driving conditions suggesting something isnt quite right. Anyway, link to the thread below for the videos of what I'm experiencing - https://www.pistonheads.com/gassing/topic.asp?h=0&f=48&t=1285949 PS - Im discounting the SAI as this noise is constant, not just on startup but please advise if you think this may well still be the culprit. Any suggestions or advice gratefullly received as its somewhat putting a dampener on what is otherwise a fantastic experience for my first Porsche! TIA - Rob

Is the whine engine related? i.e. does it whine at standstill or only when driving? If when driving then it's likely to be gearbox drivetrain related. Has the gearbox oil been changed? I'm assuming it's a manual for some reason.

Thanks for the reply. I believe its engine related as it whines at idle. I suspect I also have a transmission whine but that is separate to this whine (it appears Im collecting them!). It is manual & the gearbox oil was changed post PPI as part of a service I had before collecting the car.

I would, as your friend mentions, remove the belt and run to see if the whine goes away, then at least you know where to start your investigation. Also could it be pulling in air ie from the AOS or oil filler cap? You can also unplug the SAI to eliminate that. If it still whines there is a chance it is coming from the gearbox, does the sound go if you dip the clutch, this can be related to the clutch bearing or the input shaft?

Thanks. I removed the belt and the whine was still there. I've removed the oil filler cap before and the idle drops/fluctuates so assumed there weren't and leaks there. Where is the SAI located as I think thats the next thing to check? The whine is still apparent when you did the clutch - as mentioned above there is a separate whine relating to the transmission but nowhere near as bad as this one!

The SAI is to your immediate left as you open the engine lid, looks like a fan housing with a rubber pipe coming from it

That's what I thought from looking at other posts/videos online but I don't appear to have one?

My 98 Cab doesn't have one either. They came later and are just to meet stricter emissions, so some countries may have had them earlier than others. If it whines without the belt on, we can rule out AC comp, Alternator, pulleys, tensioner bearing and I'm guessing water pump. Does it change with revs? It's not the engine bay fan is it?

It does change with revs. Interesting you mention the fan - been meaning to look at that as the temp gauge light flashed at me on a top speed run adn after ruling everything else out read that it happens when the engine bay gets to hot so to check spoiler & engine bay fan - spoiler works but assuming the fan would be constant anyway and not change speed with revs?

As you were talking about an SAI I assumed you had a 3.6 car and not a 3.4

Apologies, was reading a few sites this morning trying to establish possible causes and hadnt seen it was engine specific! Easy to rule that out at least

The gearbox whine could be a pinion bearing as they are known to fail, but it's identified by dipping the clutch (as this should stop the whine) & will get louder over time and be noticeable when you lift off the throttle. Pinion bearing replacements are a bu**er as you need quite a large capacity press and many gearbox companies don't seem to have them anymore. Hopefully Demort might be along shortly and he'll be able to offer his advice as he's our resident 'Porsche Doctor".

Thanks. The gearbox whine will be the next thing I worry about, or not if its quiet in relation to this one, until the clutch needs doing at least. I've read several people say the 3.4 engines whine normally anyway, this just seems excessive.

Are you sure about the dipping the clutch bit? My box at 122K is whining and I plan on removing it soon to give to a specialist gearbox rebuilder. I assume pinion bearing too, but mine still makes a noise, albeit quieter when coasting with the clutch depressed. I thought the pinion bearing supported the pinion cog which drives the diff, so still turns when you press the clutch?