There are several cooling fans that are set up to operate when the car is shut down. Some of the electronics are located under the hood, adjacent to the engine, and the temperature will climb when the car is shut down, after haven been driven. There is no natural air circulation, because the car is not moving. The engine and the exhaust system continue to release heat, as they cool down. This causes temperature to climb under the hood, for something like 10 minutes. Then it gradually declines. My S60 has a fan that cools the ECM, Engine Control Module, and the TCM, transmission Control Module. The fan should not run for more than 30 minutes, unless you have parked the car in Death Valley, and the outside air temperature is around 130 degrees F!

 

My '15 S60 T6 RD does that as well. Always has and no battery issues, so I assume normal. I was also freaked out the first few times the e brake auto engaged/disengaged after parking which I guess is normal, too.

 

My KitchenAid convection oven does the same thing.

Engineers are the same everywhere, I guess.

 

Next time it happens and I catch it, I'm going to try and pop the hood & trunk (hopefully it doesn't just stop when I open the car), but I'm fairly confident it's not coming from a cooling fan for any of the under-hood modules. I specifically put my ear next to the cowl because I used to have a P2 S60 and that HVAC system would occasionally run after the car was shut off to eliminate moisture in the system. The noise was not originating from the cowl/hood area, and it seemed the loudest when I got down and listened under the car from the rear. Having been under there before, I don't remember seeing anything that had a fan on or near it, but I also haven't taken apart all the mid-under body trays so it could be hidden as well. Doesn't really seem to correspond with hot outside temps either, as both times I've heard it, it was at night with ambient temps around 75-85F, but I have had other instances of coming home from a long drive during 90-95F heat and didn't hear it then.

 

If from rear it is most likely the parking brake motors winding. If the parking brake isn't used often, the car will run the motors from time to time so they do not seize. Another noise from rear that sometimes you can hear is the Diagnostic Leak Detection Pump. As long as noise is brief and stops after locking car and there are no warning messages, I would imagine everything is fine.

 

Definitely not the electronic parking brake. I have heard the car trigger those once or twice before to eliminate slack in the rear pads and/or reduce the chance of the motors seizing, so I'm familiar with the sound the e-brake makes and that this cycle probably last 5 seconds max. Whatever is making the noise is continuous for at least a few minutes. Both times I've heard it, I've interacted with the car which stopped it, so I can't say how long the noise actually would continue for if left completely alone. Leak detection pump is a great suggestion, as it sounds very similar to how that might sound, but again, that is something that I can only see being a 5-10 second cycle, and not 2-3+ minutes.

For anyone else who is stating their cars do this, if its no trouble, can you try to pinpoint if your noise also sounds like it's coming from the rear of the car, and how long the noise last? Like I said, I'm not terribly concerned with it since I'm sure the car has its own systems in place to avoid excessive battery drainage, but I definitely want to know what the actual source is, and why it would need the pump/cooling fan on for that amount of time after shutdown in "average" ambient temperatures and non-aggressive driving (cruising at 60 mph for about 10 miles with limited stoplights)

 

My car does this, wife thinks it's weird, I figured it's normal with fans and pumps and things doing a cool-down routine, and never thought much of it.

I may just be used to these sorts of noises, though, as I had a turbo timer on my MR2 which kept the engine running for 30 seconds after I removed the key.

 

Mine does this now and again, sounds like it's from near the rear wheels to me. It's only done it a handful of times though, next time I hear it I'll try to get a recording.

 

I have three P3 cars and they all do it - perfectly normal. I can't tell you what it is but it sounds like it's coming from the rear of the car.

Not related to this but I recently installed semi-permanent trickle charger connections on 2 of the cars because they're just not getting any use.

 

So I ended up hearing the noise again a day or two ago. I immediately grabbed my creeper and tried to slide under the rear of the car (while trying to avoid the hot exhaust/muffler since the car was still on ground level) and recorded the sound as best as I could. I know the video is bad but I was just trying to get an idea of the area the sound was coming from, and it sounded the loudest while my phone was close to the rear diff/Haldex unit.

Let me know if this is the sound everyone else is hearing. The sound went on for about a minute total before it stopped itself with no interaction from me.

 

Let me know if this is the sound everyone else is hearing. The sound went on for about a minute total before it stopped itself with no interaction from me.

If from rear it is most likely the parking brake motors winding. If the parking brake isn't used often, the car will run the motors from time to time so they do not seize. Another noise from rear that sometimes you can hear is the Diagnostic Leak Detection Pump. As long as noise is brief and stops after locking car and there are no warning messages, I would imagine everything is fine.

I'm pretty sure this is the Diagnostic Leak Pump that Oceans60R referred to above after listening to the noise on the video, this has been brought up before on the forum as I had the same question a couple of years ago when I first got my V60 into the garage. The diagnostic check runs after shutdown, I believe it's pressurizing the fuel system once the car is stopped and once it reaches a specified pressure it stops the pump and monitors the pressure for several hours to look for pressure drop/leakage. If you interact with the car at all it stops the pump/check as it can't be run while the engine is running, in that case I assume it'll just wait until the next time the car is turned off and try it again. I'm not sure how often the check is run, I've heard it several times before but it doesn't appear that it runs every day.

 

Mine did it today, the noise in your video is exactly the same.

 

I was going to say, grab that pump that is white on the top and see if that's the noise maker. Thats your DMTL pump. Its a normal function if its that pump which sits right next to the haldex on the rear subframe.
I will say that they usually aren't that loud so it could be on its way out. If/When it goes bad, there will be a CEL for that.

 

Given that the sound was the loudest when my phone was near that pump, I'd say you (and the others) are right, and that is the source of the noise.

So, with that piece of information out of the way, I ask my next question. Is it normal for this pump to have to run for 1 to 4 minutes (it seems to vary every time I pay close enough attention to the time it takes to shut off without interaction) to get the fuel system up to whatever pressure the leak test is run at? I mean it sounds reasonable that it would take some time for what essentially seems like a small air compressor to pressurize a few gallons of air volume, or even up to 15 gallons if your tank is close to empty (which explains the time variance) but I don't know what pressure the test is run at so it also may normally be a shorter cycle time than what I'm seeing, and that would fit the "on it's way out" theory.

 

The ECM runs the test at a determined time, so you don't really have an option as to when its going to run. There are a host of pre-conditions for the monitor to run. There is no pressure for you to monitor but you are correct in assuming the less air in the tank (more gas) it will take shorter time to achieve test results. If you have VIDA you can watch the pressure graph during the Quick Tank Test. Otherwise, if you have no CEL, there is literally nothing to worry about. Of note, test will normally operate when tank is between 1/4 and 3/4 full.