Hi there guys, I have a 2012 Countryman S. I have about 40K miles on it and for some reason, just recently I noticed a hissing sound when I shut the car off, coming from the engine after driving around. Again, I may have missed this in the past, as I have never heard this before. I recently had the turbo replaced and right before it was replaced I started hearing this hissing sound. Dealer stated they could not replicate the noise. Well I hear it now for sure. What could it be, should it go in? I noticed in 2011 someone mentioned it, but since time has passed since I figured I'd ask again. Thanks in advance.

 

The first thing that comes to mind would be a small leak somewhere in the cooling system. If this is the case, eventually you will have to add some coolant. We had this happen in our BMW X5 when it was about one year old. It was a tiny leak… We would have to add coolant only every couple of months. It took the dealer three attempts before they found the problem, and that was only after they added some special dye to the coolant that would show up under a special light. Turns out there was a tiny pinhole in one of the hoses, and the reason it was so difficult to find is that it was out of sight, and the leak was so slow that the escaping coolant would evaporate rather than drip and/or leave residue.

 

I believe in the S models the car will run a small pump to cycle coolant through the turbo to help cool it after the engine is shut off. Can't say for sure that's what you're hearing, but I know when I first heard my R56 do it I thought it was a coolant leak. My R61 does it as well. If you're in doubt though it can't hurt to take it in, especially if you've had problems with the turbo in the past...just make sure you can replicate the noise. You can always ask to be there when the service guy takes a look to point the noise out. I did this when I took my R56 in for the timing chain...no way they could deny it then.

 

Good tip Arsci, I will definitely be taking him in just incase as Shark715 mentioned, it's a cooling system leak or if it's something else. I noticed that it does not happen when I drive in the city at the regular in town speed limit. If I drive on say, the interstate for 3 minutes and pull into a parking lot and shut the car off, the hissing is there. Indeed you may be right, it may be induced by the Turbo engaging at some point which may not happen in the city. That's my guess. Anyhow, I recorded the sound in video for the dealer and thankfully was able to replicate it by driving it at above the in-town speed limit. This should help me explain to them how to replicate it. I too have a Cooper S and it doesn't make this sound. And it has had the turbo replaced twice; a whole other story. With that said, I did get the hissing noise to engage, it it's coming from around the Turbo area for sure. I also noticed in the underbelly there's a white wire connected to the catalytic converter sensor, and if I touch that wire, it's vibrating. So I'm not sure if there's an electric current going into the wire, feeding back to where that hissing is coming from. May tell me if it's intentional or not. For now I'm just not sure and trying to collect clues. Curious me.

 

There is a pump as Arsci mentioned, and that might very well be what you were hearing, although I would describe that noise as more of a humming rather than a hissing. You can hear the pump running on our car every time after the engine is shut off, even if it is been driven only a mile or so on local roads.

 

Ok, so car is in the shop now. Stayed there the weekend as they wanted the master tech to take a look at it. Will keep this post updated on any developments.

 

Well car has been in the shop for 4 days now and still no update. Not going to assume it's a horrible thing, but doesn't seem all too good.

 

So here's a video of the hissing sound.
As previously stated, the shop has been trying to diagnose this issue without much success. They have admitted that nothing comes up in the diagnostics and that they can't replicate the noise that's obvious in the above video. I've had far too many frequent issues with my coopers to dismiss any noise, regardless of how faint it is. Any hints will help. Thanks.

 

Sounds like a coolant leak (to my untrained ear). It's definitely not the same noise as the hum that our auxiliary coolant pump makes. But, if it was a coolant leak, no doubt they have the equipment to pressurize the system, and find the most minor of leaks. Given that they can't duplicate the hissing, it must be something else. Perhaps a leak in the evaporative emissions control system?

 

Mine does the same, I think it is a pump to cool the turbo. I released the pressure in the coolant system and it still made noise.

 

Alright guys, so finally looks like the shop foreman decided that replacing the water pump connected to the turbo will help. He's under the impression that this part may be faulty and emitting this hissing sound. It'll provide peace of mind nonetheless. Getting the fan look at too because it doesnt seem to ever turn on.

 

Most definitely not the pump cooling the turbo.

 

Finally someone that has the same issue. The aux water pump was just replaced today. I would have been content with the shop letting me know it was normal. Unfortunately, they felt that was not the case. I'll update on how this fairs out and if even with the new aux pump the hissing still remains. Hopefully this thread helps others.

 

Did replacing the pump eliminate the noise?

 

I would say yes with a footnote. I've only heard it once and it was extremely faint and went away in less than a minute after turning off the vehicle. So in my book, it's pretty much gone.