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Discussion Starter #1
I'm getting a very intermittent, quite loud clicking noise from the engine bay. To me the noise sounds like a solenoid or actuator of some sort that is pulsing on or off, causing some valve or flap to slap back and forth. The sound you get it you manually 'ping' the valve on the intake plenum is quite similar but the actuator does not appear to move when the noise occurs. I have once managed to video the noise but not managed to pin down the precise source. Here is the video:


Notice that the noise continues for a couple of seconds after the engine is stopped.

Once started the noise will continue for 3-4 minutes and then stop on it's own. If you turn the engine off it behaves as in the video and stops shortly after the engine. The noise occurs very infrequently, I've run the car for 4 hours straight without hearing it, but one time it started 15 minutes after leaving home. The noise it totally independent of engine speed. Adjusting the HVAC controls makes no difference at all.

On a separate occasion I have heard a similar noise which occurred about every 10-15 seconds when the engine was stopped but ignition in position 2. As far as I could tell it was coming from the box that is between the brake fluid reservoir and plenum, it has a cable attached to it that goes to the throttle mechanism. The only thing I can think it is would be the cutoff speed control. This is the box :





Does anyone have any idea what this noise might be and what might be causing it?
 

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Richard,

Very serendipitous that you would post this. I'm having a similar issue with one of my own M5Ts. This same type of clicking/pulsating that is wildly inconsistent: doesn't occur, begins at start-up and stops after a few minutes, begins at start-up and persists, arises out of nowhere while driving, and/or continues for a few seconds after shut-off. In my case it is definitely the Vmax-limiting bowden cable actuator, which is what you have focused on in the last photo. If I put my hand on it while the noise is occurring, I can feel the pulsations in synchrony with the noise. In no instance have I seen the cable actually move, nor has it limited the throttle in any way. Immensely annoying, however. I'm not sure if it's the actuator itself that is faulty, or if the Vmax control box is faulty, or if there is a sensor somewhere in the system that has gone wonky. Would love to hear anyone else's input with such a problem. I've been trying to figure out a way to remove the system in its entirety.
 

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Discussion Starter #3
Glad (in a perverse way) that I'm not alone. Hopefully between us and the vast knowledge on this forum we can get to the bottom of it.
 
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