questions from a new 993 owner

[irhmsd]

I recently purchased a 1997 993 cab and am not sure about a couple of peculiar noises. Thoughts are welcome.

1) After I turn the car off, I can sometimes hear a buzzing or fan run in the dashboard for about 10 minutes near the a/c control panel. Is that normal? I thought it may have been a groaning clock, but that is not it. There is no smell present, like burning wires or anything.

2) When I leave a traffic light and shift through the gears, as I get into third and climb from about 42-47 mph, I can hear a mild whir from the rear end. The sound is faint at best and typically more audible if the convertible top is closed. If I modulate the gas, the noise dissapears. Once the noise goes away, I can stay in third and climb and decel in the 40 - 50 mph range and not be able to reproduce the noise again - that is until I stop at a light and start climbing through the gears again. Sometimes you can hear the noise in second gear for a second or two at about 3100 rpm. I thought it was tire roar (18" wheels) or noise from the tranny or engine but if that where the case, I would think you would always hear the noise at the speed that provokes the noise. I also suspected it was the spoiler deploying but it always happens below 45 MPH which is 5 MPH short of when the spoiler goes up.

3) When cold, the engine has a whistling noise. It sounds like wind whistling through the trees, most obvious when you shift from first to second. The noise goes away when the engine warms up a tad. I thought it was belt squeal, but the noise is much more like a wind noise. The car has the motor sound package if that helps.

Finally, the car has 62K and the top end was fully rebuilt by Porsche 5K miles ago. The car runs like a clock, and though has these wierd noises, runs like a champ.

[Richard Hamilton]

I can't comment on 2 or 3, but 1 is normal. There is a small fan on the back of the AC control unit, which blows air over the temperature sensor. The fan runs for a few minutes after the ignition is switched off. These fans are prone to failing, which makes temperature control erratic, but if yours is running that's good!

[irhmsd]

I can't comment on 2 or 3, but 1 is normal. There is a small fan on the back of the AC control unit, which blows air over the temperature sensor. The fan runs for a few minutes after the ignition is switched off. These fans are prone to failing, which makes temperature control erratic, but if yours is running that's good!

Richard:

Thanks for the reply man! I have had a coupe of folks surmise that the noise in the dash was normal so that is cool. The other two noises are not serious but I was wondering if there was some sort of explanation. It will sort out soon. The car is just new to me.

Ivan

[irhmsd]

I can't comment on 2 or 3, but 1 is normal. There is a small fan on the back of the AC control unit, which blows air over the temperature sensor. The fan runs for a few minutes after the ignition is switched off. These fans are prone to failing, which makes temperature control erratic, but if yours is running that's good!

Richard:

Thanks for the reply man! I have had a coupe of folks surmise that the noise in the dash was normal so that is cool. The other two noises are not serious but I was wondering if there was some sort of explanation. It will sort out soon. The car is just new to me.

Ivan

I wanted to let everyone know what I learned about the noises at the Porsche Dealer today, Holberts in Warrington, PA.

1) The noise in the dash is in fact normal. It is the small fan in the climate control panel that blows air over the sensor to let the car know what it should be doing to hold a steady passsenger compartment temperature.

2) The whine in the rear is the secondary air fan clutch kicking in. I took a drive in the car with Bobby Holbert who has been working on Porsches for an age and he said the noise is totally normal, not to worry.

3) The whistling wind noise, more of the same, can be seen as relatively normal. It is some system that runs for the first 10 or so minutes of the car's operation when cold to help burn off excess hydrocarbons.

There you have it!

Ivan

[irhmsd]

I have an update on the engine "whine" that was occuring between 2900 and 3100 RPM. It was not a fan clutch at all! It was an alternator that was starting to go bad. I had the alternator replaced today and the car is noise free! I knew that noise did not belong there.

The only thing left on this car is an intermittent rough idle. The car feels very similar to me at idle as my previous 87 and 89 carerras but the dealer said it felt a bit rough to them, then it straightens itself out. They checked all kinds of things like plugs, plug wires, distributor and even plugged it up to the computer for quite a spell and found nothing. They surmise it could be the mass air sensor but since the computer showed nothing they just cleaned it and said wait until it becomes more severe or trips a light on the dash, which they said may never happen. They said the rough idle could be some of the ethanol in the gas in the area as they have seen that before. I put some injector cleaner in the car and will try a different type of gas for the next tank and see what happens.