"Air Compressor" Type Sound from Rear of V8 Vantage
 

Hi fellas,

I am hoping you guys can help me diagnose a new sound that I recently noticed.

I just took my '09 V8V out for an hour-long drive at night after work (temperature here in the Bay Area somewhere in the mid 50s). After coming back to the garage and turning the car off, I noticed this "air compressor" sound coming from the rear of the car, specifically from the driver's side along the rear tire. Could this be something related to the gas tank or exhaust system?

The only mod that I have done to my car is having my local AM dealer clamp some hose to the exhaust so that my car is constantly in "loud" mode without having to remove a certain fuse in the trunk.

The sound lasted for about 1-2 minutes. Below is a link to the video I just took. The noise is definitely coming from the rear driver's side area. Again, my car is turned completely off.

Sounds to me like the gearbox lube pump running on
Probably because the oil is hot
(as is the car from the popping ;) )

ETA is it a sport shift? Do you get the same sound as you open the drivers door after unlocking it?

that's interesting....i hadn't noticed this before after my other long drives. in response to your question mikey k, my car is a MT, not a sport shift. Would this make a difference?

Yes. On a SS there is a electric pump that moves the fluid around the shifter unit, but both MT and SS are cooled with hard lines and a cooler seperate from the ASM.

It could be the DTML pump running. They have a buzz noise when they running and are in the driver side fender well. But while off?!....I do hear alot of exhaust popping.

Not to be mean...but is it a chance that it is the cooling fans running and you hear it in the back? To me it sounds like the cooling fans are running. They will stay on for a few minutes after a hard drive with the key off.

For the first time in over 2 years of ownership, I heard the exact same noise after shutting off my car this evening. It ran for about 2 minutes and was not the fan.

I walked around the entire car, listened in the trunk etc and the sound was near the rear driver wheel. It stopped 2 minutes in as quickly as it started.

Car is 6speed manual as well

I am glad to hear someone else report this as unusual. I never had this happen on my 08 sport shift but on my new 09 MT I noticed it twice now after normal drives around town. I drove it 3000 miles back from Dallas to Seattle without noticing anything. It sounds like a small compressor pump running inside my rear drivers side tire. It happened twice and ran for about 1 minute then shut off.

ok; looks like we are all hearing the same thing....and we are all driving a MT. I heard this noise for the first time in about 1 year of ownership.

anyhow, I sent the video file off to my local AM dealership. the service rep. seemed to think this was normal, something to do with the fuel pump he said. but, he's gonna have his tech. listen to the file and they should hopefully get back to me tomorrow.

for what it's worth, i did some quick research into the DTML pump after reading AMFixer's post. could not find anythign specific relating to AM, but from a BMW forum, it appears that the DTML pump is different from the fuel pump. the DTML pump is used to perform an occasional diagnostic leak check of the fuel system. the DTML pump pressurizes the fuel system and the the car's computer verifies that the pressure is held. on completion of the test, the pressure is released. sometimes this process occurs after the car is shut down, which could explain the noise. perhaps this also applies to Astons?

Yes same thing for thr Aston's. But I have never heard one go off after turning the car off. Not to say it couldn't happen :confused:. I really don't think that's the noise, nor do I think it's the fuel pump. Again the key and engine are off right? Both require a ignition switched power to even operate, let alone a signal from the ecm. Let's see if I can get irish07 to have a listen. Maybe he has heard it before.

To me it sounds like the DMTL pump running a check. The system does actually run at times while completely "off". The vehicle has to go through a number of steps (drive cycle for DMTL pump), when this drive cycle is met, the test is performed, weither it be a small or large leak test. The large leak test is usually done while running(how it detects a open fuel cap), the small leak test is usually done while off. If a leak at say 20thou was present on a purge line(small pin hole from some road debris), the DTML would not detect this leak while running for the vapour mangement valve opens/closes while running and fuel level changes and does not stay steady(flat), due to stop-go and corning..so for a small leak, the small leak drive cycle has to be met and vehicle needs to sit while off(soak for time). When the car was just turned off, the large leak test will still continue if it had started and will stop when it finishes(don't have to worry about the battery, it has a protection for that is low voltage is present so the test does not fail)...if you just shut off the car and the noise continued to be heard for 2mins..this sounds like the large leak test was in operation-and continued till finished. If there was a fault with the test, next ignition cycle the MIL light would be on..no fault, no MIL light

That's why I never heard one go off. I test drive cars after repairs, but I dont drive them hard or long enough to meet the standards for the test.

Thanks for the help Irish and Fixer, good to know it seems normal.....even with car off and key out!

I'm sure Irish only knows this from second hand experience. C you'd never be out there hot testing any client's car woulda ya now? hilarious

Hehe...I'll never tell :D

thanks everyone for your help diagnosing this. have not heard back from my dealer yet, but that doesn't matter since we have access to AMFixer and Irish. :)

if my dealer gets back to me with a different diagnosis, i'll report back.

Sorry I couldn't report back until now, but mine did happen after I was back in my garage with the car turned off and the key out. That is probably the only reason I would be able to hear it was when the 420 ponies were sleeping quietly. So it sounds like this is normal and nothing to be alarmed about. Thank you to our friends Irish07 and AMFixer!