Loud, high-pitched whine!

kirk knighton · Posted: Wed Jul 08, 2015 2:34 pm Post subject: Loud, high-pitched whine!

Weird as hell! It starts once the engine is warm. Sounds like it's coming from the front of the plenum. When you punch the accelerator it goes away momentarily, so I'm sure it's some kind of vacuum leak. I've taken everything off to the plenum - air cleaner, all the hoses, etc - and then started the engine, and the whine is still there. Everything looks good and feels rock-solid tight. Where oh where is that shrieking whine coming from?

Oh yeah, this is my 1971 411 wagon with D-tronic FI

raygreenwood · Posted: Wed Jul 08, 2015 5:25 pm Post subject:

Check the o-ing between the TB and the plenum. Also check the, cork gasket at the oil breather. Ray

Lars S · Posted: Thu Jul 09, 2015 4:28 am Post subject:

Check the manifold pressir sensor (MPS) for air tightness....I had a similar noise once and it was a crack in the MPS membran.

Lars S
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raygreenwood · Posted: Thu Jul 09, 2015 5:57 am Post subject:

Ooooooh...yeah...great suggestion. I have only had that happen once a long time ago.its a strange sound.
Ray

kirk knighton · Posted: Thu Jul 09, 2015 11:08 am Post subject:

is that the thing mounted over in the left side of the engine compartment?

Lars S · Posted: Thu Jul 09, 2015 11:24 am Post subject:

Lars S · Posted: Thu Jul 09, 2015 11:26 am Post subject:

Try sucking where the hose attaches to it...should be 100% air tight....or listen if this is where the noise comes from

Lars s
_________________
Porsche 914 -72, Bahia Red daily driver Smile

VW411 2-d -70, White, sold Sad

VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold Sad

Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold Sad

Husqvarna 118cc, -47, Black, Sold Sad

kirk knighton · Posted: Thu Jul 09, 2015 12:52 pm Post subject:

okay, it's not that then. The noise is definitely coming from the area of the throttle body/plenum. I've taken off the boot to the TB and now it sits naked and open. And still the whine! Which goes away as you punch the gas pedal. All the screws are tight; nothing feels loose. Do I need to remove the throttle body? Is this hard to do?

ClassicCamper · Samba Member Joined: December 17, 2002 Posts: 679

raygreenwood · Posted: Thu Jul 09, 2015 8:15 pm Post subject:

Look for one for a 2.0 bus TB. Its slightly, different but, works. I use a very thin even smear of high temp permatex ultra...any of them will do for this but ultra black or copper are best. Adhere the cone shaped gasket to the TB...tape it in place to keep it straight, and let dry overnight. Reach in with a q-tip and clean out any RTV that squeezes out becore it, dries.
Then put a thin smear on the plenum side install and let dry completely. Ray


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