"Flapping" sound at idle

[sbc17]

I have a flapping sound at idle. It sounds like a fan hitting something but I can't narrow it down. When I press in the clutch the sound goes away. This makes me think its something going bad in the clutch. Any thoughts guys?

-sbc

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[BC_ZX3]

Chattering clutch throw out bearing possibly. They get noisy but seldom fail in a catastrophic way. It's play in the bearing. When you depress the clutch, the bearing slack is taken up.

[sbc17]

Alright. It just started happening within the last couple days. 78000mi. How much $$ and how much longer can/should I drive on it.

[whynotthinkwhynot]

Most people refer to the throwout bearing noise as a knock. You might want to search online and familiarize yourself with how a hydraulic clutch works, and how the parts are put together to alleviate your concerns. I can give you a brief write-up. On the back of the crankshaft is the flywheel. The pressure plate is bolted to the flywheel, and is a big giant spring with forks that point towards the center. When the forks are pushed, the spring releases. Underneath the pressure plate is the friction disc that the pressure plate forces against the flywheel to mate the engine and transmission. The input shaft of the transmission fits through the hole in the pressure plate forks, and the friction disc fits on the input shaft splines. The slave cylinder is what converts clutch pedal travel to force on the pressure plate. The slave cylinder sits around the input shaft, and doesn't rotate like the other parts. The throw-out bearing is what is between the slave cylinder and the pressure plate to allow a moving part and a part that doesn't move to meet without damage.

In this particular case (and a great many others), you have a metal bearing glued to a plastic slave cylinder. Eventually, the glue breaks away, and the throw-out bearing rattles between the slave cylinder and the pressure plate. How long will it last? Mine has lasted about 100k miles since it started rattling. It doesn't hurt anything- it just makes a noise that goes away as soon as you press down on the clutch pedal which pushes the throw-out bearing into the pressure plate to release the friction disc.

[sbc17]

Wow, thanks for the write up. I guess I could call the noise a "knock". This gives me some reassurance for replacing it. I have to park the car this winter(can't afford winter tires right now) so I will probably take care of this early next spring. So I take it I would have to replace the whole slave cylinder huh?

-sbc