Buzz/hiss coming from the fromt of a 986
 

Hi.
I am now to this forum and not quite techie, just a word of warning. ;)
My Porsche 986 Boxster, 2.5, 1998 has developed a fault which so far doesn't look to be too major, but is quite annoying at least.
There is a noticeable noise coming from the front, it seems somewhere just behind the main console. It doesn't seem to be connected with the operation of the air conditioning, since it is there even if the AC is off.
It changes its frequency according to the revs of the engine - starts as a faint buzz and when revving the engine up or accelerating goes to high pitch whizzing. It doesn't depend on the speed but on the revs of the engine alone. Sometimes it is not there at all, sometimes it is quite noticeable.
Could it be something to do with the dynamo? Or could it be the clutch, which I have replaced recently? Or as far as I know there's some fan there, could it be faulty?
Any recommendations of how this could be fixed will be very welcome.
Thanks!

I don't know what a dynamo is...
Clutch noise would be be behind you not in front.
Is your radio on? AM by any chance. buzzing that rises and falls with RPMs can be electrical noise coming through your radio antenna ground.

Good suggestion dghii. The dynamo would be the alternator and, as with the clutch, any noise would be coming from the rear and not the front of the car. Radio interference can easily increase and decrease in intensity with engine RPM's, unlike noise from the fans for the radiators or HVAC system, so that would be my best guess as well.

My car makes a buzzing or whining like noise from the front when the AC is on. This happens even when the temperature is set so there is hot air coming out of the vents. Porsche runs the AC to dry the air being circulated in the car even when heating.

Try this to see if the noise is AC related. With the engine on and the AC snowflake showing on the LCD display, listen for the noise. If you hear it, push the snowflake button on center console so that it the snowflake disappears on the LCD display. If the noise goes away, then it's AC related. Most likely, it is coming from the expansion value of the evaporator. One is cheap to fix. The other is costly.

Look inside your fuel door on the right fender. With it open look to the front side of the opening and you will see vent holes. There's some fuel vapor switch that fails inside the fender that you can fix and it will stop the sound. I put black duck tape over the holes and have put on 10K miles with no check engine light. Buzz/hiss sound gone. I'm 100% sure that's what you are hearing. If you search around with that in mind you will see some write ups with part numbers and prices and how to change it out. Wasn't worth the effort to me you will never know the duck tape is in there. : )

Thank you very much for your responses, folks. Much appreciated!
It is definitely not the radio (I'm not a complete idiot, I hope), neither the AC.
It could be this thing with the fuel door - I will check and report.
The thing is this sound follows exactly the revs of the engine. It must be some sort of belt or something which depends on that. I don't know... It wasn't there the last 3-4 times I used the car and yesterday it was back. :mad:
I hope my English doesn't make things more complicated.

Naaahhh , these cats love us English boys!

Wan't trying to imply you were an idiot...trying to troubleshoot sounds over the internet is pretty tough. Just trying to eliminate possibilities. Good luck.

If you are confident it isn't the AC, then I won't comment further other than to say this.

There are no belts up front that would make the sound coincide with engine speed. The reason I suggested AC is that the flow of refrigerant in the AC system is related to the speed of the AC compressor. And the AC compressor is driven by a belt back in the engine compartment. The AC noise I mentioned in my car changed with engine speed until I turned the compressor off using the snowflake button.

Figured I'd find the rest of the detail for you since it seems to be less common of and issue then I thought. Part # 996 605 213 01 again tape over the hole is all it takes to stop the noise. Someone's picture of the hole I'm talking about at the fuel door. Item 9 in the parts list view. This is for the kazoo, howling, blowing into a bottle sound that changes with RPM, load and speed.

To add to this the main console you are talking about is the dashboard or shift area not the armrest or behind the seats.

Thanks!
 

Hi. Sorry for getting back to the discussion with such a lenghty delay.
I attampted covering that hole, but tis didn't solve the problem.
dghii seems to be right by suggesting the the noise seems to be connected with the radio operation. :cheers:
The thing is the noise is there only while the radio is OFF, as soon as I put it on, it goes away. Weird, innit?! I guess I need to have it checked... or just continue listening to my favourite tunes at all times. :ah: