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I own a 2008 Euro Civic Type-R which has almost the same engine as the US Civic Si (K20Z3 vs K20Z4).

Since a bit of time I have a really annoying high pitched noise coming from the engine. It's constantly present, completely tied to revs, and persists when clutch is disengaged (so it's not coming from the gearbox). It sounds a bit like an electric motor from a radio-controlled toy car.

About six months ago (maybe a year) the sound could not be heard inside the cabin when cruising unless windows were open, but started being heard when opening the windows, especially in an underground parking lot. I brought it to the dealer who said it was normal engine noise, and that "fixing" it would require a new engine (quotes meaning that it was, to him, not requiring being fixed).

The sound is stronger now as I can hear it in the cabin when cruising with windows closed, to the point of being distractive, if not painful on long journeys, so I don't really buy it that this is normal.

THe car is completely stock. I'm running on 0w40 oil, am regularly pushing the car but have always respected warm up time, and since I bought the car new, did (to the best of my knowledge) proper break-in. FWIW the K20 engine has a chain transmission and an accessory belt.

Here is a video recording where I rev at a standstill, with clutch disengaged (watch in 720p HD for clearer sound).

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I would go to the dealer and ask if they have a similar 2008 you can test drive or at least start and rev to see if it makes the same noise. – mikes May 20 '12 at 10:37
Do you still have the car with this problem? – DucatiKiller Feb 21 at 4:00
Yes, but the noise largely went away over the years although I could not pinpoint why. For the record I recently (a year ago) went from from Mobil 1 to Motul 300V (still 0W40) and the engine generally behaves much better. – Lloeki Feb 22 at 8:10
I had a high pitch whine directly tied to engine RPM that I eventually narrowed down to a bad ground in the aftermarket auxiliary jack, as the sound did not occur when the stereo was offf, or when listening to a CD or radio. It doesn't sound like that's your problem seeing as it's more noticeable in a parking garage, but I figured I'd comment as a troubleshooting method for future readers. – MooseLucifer Mar 23 at 17:15

Have you checked the Power steering pump/fluid level? I own a 2003 stream and heard a slightly heavier whining noise similarly tied to engine speed. You could try turning the steering end to end while engine is idling and listen. In my case it turned out to be a defective power steering hose.

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Nice try, but power steering is electric on this car. – Lloeki Feb 22 at 8:10

Can you hear where in the engine it's coming from or at least what area? Since the noise is tied to engine revs, I'd suggest checking anything that increases with increased RPMs. Power steering pump/fluid levels, timing belt/chain, tensioners, AC compressor, alternator, etc.

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Open the hood and listen. You can find an automotive stethoscope for more precision. If it's coming from the engine itself, try changing oil weight. If it's coming from the pulley on the left, you could try replacing the pulley. If it's coming from around the throttle body, check for vacuum leaks.

For oil weight, try 30 weight oil. Here in the states, we use OE 5W30 (as stated on the oil fill cap). You can also try using a Honda OE oil filter for improved flow rate.

The pulley thing happens on my FA5 (K20Z3). It's the idler pulley that replaces the hydraulic power steering pump since we have electric power steering. I had the pulley replaced with a new one, but it didn't change the sound.

Vacuum leaks could be coming from the brake booster hose or maybe the crank case pressure hose. Just replace those hoses if you suspect they're the issue.

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The noise largely went away over the years although I could not pinpoint why. For the record I recently (a year ago) went from from Mobil 1 to Motul 300V (still 0W40) and the engine generally behaves much better. – Lloeki Feb 22 at 8:12

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