[Mgs] Whistle from anti-run-on valve

[PaulHunt73]

The factory anti-runon system is passing air all the time the engine is running, to purge the charcoal canister and crankcase using the suction from the carb(s).  When you turn off the ignition the valve closes, which allows a higher level of vacuum to develop in the plumbing, and that sucks the fuel out of the carb jet(s) to prevent running-on.

So if any of the many components, hoses or joints in the system are leaking it could create the noise you are hearing.  You can pinch off various hoses and if the noise stops you know the source is beyond that point, and can move on to the next.

It could, of course be a number of other things like fanbelt, fan, water pump, alternator etc.

PaulH.

  ----- Original Message ----- 
  But I've noticed when I rev the engine to 3500rpm between shifts, there is an odd whistling noise that comes from under the hood. Sounds like it's coming from the anti run on valve area, but I can't confirm that. 
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