Strange noises from my 986

[perleman]

Hi everyone, first post!

My boxster has some odd noises.

1: whine / whistle only in 5th gear between 84-89MPH. Stops immediatly on removing foot from gas. The car has never had manual transmision oil changed (9 years old, 40k miles) and I'm wondering if the level is a little low. Am planing on doing this tomorrow as it's relatively inexpensive c. £80. It's not an air noise and I doubt it's a failing alternator as the sound stops dead on removing foot from gas pedal. Just spotted the thing about the vapour recovery vacum but surely that would continue regardless of whether foot is on gas or not?

2: rattle on ULTRA hard acceleration in 2nd and 3rd gear. Pottential causes could be corroded material in baffle, engine mount, loose oxygen sensor, loose heat shields, some other exhaust related issue.

Can anyone shed any more light on these issues? Any insight appreciated!

Edited October 19, 2007 by perleman

[pk2]

Hi everyone, first post!

My boxster has some odd noises.

1: whine / whistle only in 5th gear between 84-89MPH. ...rattle on ULTRA hard acceleration in 2nd and 3rd gear. ...

If your whine is indeed from the trans, damage is probably done and changing the gear oil will only arrest it’s progression.

For what your spending, you might find someone willing to put it on a lift and wind it up to 86, and poke around with a tube (to his ear)…see if he can find out where the wine is coming from. Same with rattle

Regards, PK

Edited October 20, 2007 by pk2

[Glyn]

Hi everyone, first post!

My boxster has some odd noises.

1: whine / whistle only in 5th gear between 84-89MPH. Stops immediatly on removing foot from gas. The car has never had manual transmision oil changed (9 years old, 40k miles) and I'm wondering if the level is a little low. Am planing on doing this tomorrow as it's relatively inexpensive c. £80. It's not an air noise and I doubt it's a failing alternator as the sound stops dead on removing foot from gas pedal. Just spotted the thing about the vapour recovery vacum but surely that would continue regardless of whether foot is on gas or not?

2: rattle on ULTRA hard acceleration in 2nd and 3rd gear. Pottential causes could be corroded material in baffle, engine mount, loose oxygen sensor, loose heat shields, some other exhaust related issue.

Can anyone shed any more light on these issues? Any insight appreciated!

I too get a whine over 80 - but then again i know what the problem is - I simply remove the wife from the passenger seat.

Is it possible you could post a sound file to this forum as this will give us a bit of a clue.

Can you get someone else to drive whilst you sit as passenger and root around the cabin to pinpoint where the noise is comming from?

What you describe is when the engine is under load, off the throttle then the load is removed, Any chance it does this at the same revs in any other gear?

If it doesnt do this in any other gear and is speed related then i cant imagine its anything to do with the engine, possible a transmission fault but you could get the vehicle on a rolling road to simulate conditions- that way you can nail it.

The rattle on hard acceleration - are you sure ist not pre-ignition, perhaps a knock sensor has failed, if you can put a higher octane fuel in the car try it, the higher the octane the greater the resistance to pre-ignition.

Pre-ignition produces a metalic knock when under severe load (full throttle) occurs more easily the higher the gear you are in.

Pre-ignition can also be caused by a build up of carbon in the cylinders and the carbon glows which ignites the fuel before the spark plug fires, unusually high mileage may have this degree of carbon build up to cuase the problem.

The metalic rattle is the piston swapping contact points from one side of the bore to the other prior to the piston reaching top dead centre, can cause overheating and ultimately will damage the engine