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Ran my car for about 25 mins, stopped at the post office, started walking away from the car but heard a whining / humming... I almost walked away and wrote it off as something other than my car.
Then..... yep coming from the engine bay. Keys are in my hand mind you... no fans running either, I thought about that, but this did not sound like a fan at all.
Popped the hood, and narrowed it down to either this part (see picture) or something so close to this part that I could feel a vibration when I touched this part. I got REAL close to it and I swear it had to be coming from this part... OR maybe from the secondary air pump which is right behind this part????
The noise continued for all 10+ minutes I was in the Post Office. The noise did not re-occur after any of my subsequent runs.
NOTE: secondary air pump and spider hose were JUST changed, albeit used (but functioning SAI from another Allroad), the hose was new from the dealer.
On my 4.2 allroad the relay for the SAI pump went bad, causing the pump to run randomly even with the key not in ignition. Replacing the relay (standard automotive type) fixed it. The relay is in the box with the ECU under the cowl cover.
As well as the SAI there is also a secondary water pump (electric) underneath the inlet manifold in the valley of the V engine. My understanding is this pump is supposed to run on after you turn the motor off if your turbo's are hot to let them cool down with a bit of water circulation. It's only a small electric water pump, shouldn't be noticeable sound. Could that have been what you heard? Had you just stopped after a 'spirited' drive?
The SAI runs when you start the engine, usually quite an audible sound, but should not run once the engine is idling correctly. You should be able to compare the sound by checking next time you start the car from cold.
As well as the SAI there is also a secondary water pump (electric) underneath the inlet manifold in the valley of the V engine. My understanding is this pump is supposed to run on after you turn the motor off if your turbo's are hot to let them cool down with a bit of water circulation. It's only a small electric water pump, shouldn't be noticeable sound. Could that have been what you heard? Had you just stopped after a 'spirited' drive?
The SAI runs when you start the engine, usually quite an audible sound, but should not run once the engine is idling correctly. You should be able to compare the sound by checking next time you start the car from cold.
My SAI had just been changed along with a bunch of other items. I told the tech who "repaired" the car that the last shop told me I needed an SAI and relay. I was told the relay was bad due to the bad pump or vice versa. So I am pretty sure the tech ONLY changed the SAI pump (for a used one) without fixing the relay. So basically he did a half *** job. Wanna know how I know? Cuz the damn check engine light is back on only a few days after picking it up. He handed the car over to me with no CEL, clearly because the battery had been disconnected, not because he actually fixed anything.
Funny too, when I picked up the car I looked at the clock and saw that it had only been reset 1 hr prior to my getting in it. (it read jan 1 2000 1:05 AM) so the jerk probably cleared it right when I called to say I was on my way.
08-12-2015, 08:04 PM
Noise from engine when car is OFF
