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Originally Posted by usridzero
Guys, I just bought my first Porsche, a 1999 Boxster, with only 52K miles on it.
Today temperatures in NoVA were well over 100, feeling like 108. While the car was performing normal, the temperature gauge reached 200. The cooling fans were running most of the day, so I figured its all normal, right?
The concern I have now is that once I got home, and backed the car up my driveway, the car was making a rattle-ling noise coming from the back. It sounded like old valves with low or no oil. The noise was only noticeable while releasing the clutch and at low RPMs, very small rattle at idle, but not at high RPMs.
Am I making too much of it? should I be concern about today's hot temperatures? I am due for an oil change, and I am worry that the car might have over-heated and caused that rattle noise now on the back.
Any suggestions?
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Does the car have a single mass flywheel?
If you have been around one that does you will find that they clack in neutral but it stops if you push in the clutch or rev the motor.
The reason this clack sound occurs is due to the un-eveness of torque as the motor rotates through its compression cycles. There are moments of instantaneous acceleration as the individual pistons fire followed by reduced force within each rotation of the crankshaft.
With a light weight single mass flywheel, there is no additional weight to smooth out the toque as the flywheel goes around (hence the dampened dual mass flywheel).
The clack is caused by the gears tapping against each other due to the undampened rotation of the flywheel.
I suspect that in your case, due to the hot weather, your gearbox oil got hot and thin and you noticed the same phonomenon as a single mass flywheel.
If you have not changed your gearbox oil, you might consider it but otherwise the sound should go away when the weather cools off.