Hissing Sound..and it's not a Dragon
 

My 2004 MCS just developed a hissing sound under acceleration similar to the sound of blowing compressed air from an air hose. I have checked all hoses under the hood and everything appears to be normal. The sound can not be replicated by reving the engine when sitting still, it only appears when driving. Anyone had a similar issue or have any advise?

Check and make sure you're interior air filter is in tight:nod: I'm driving sans filter right now and noticed a lot more noise from the rght side of the car. Do any Mods recently?

No mods recently. Mini dealer checked the intake today for leaks and ran a smoke test to look for leaks and nothing. They are saying it may be my K&N but it's been on for 40,000 miles without the hiss. Still puzzled:confused: :confused: :confused:

You might want to swap out the K&N or just remove it for a test drive. See if the sound changes. A hiss sure sounds like an intake leak to me. Is the piping tight at the throttle body?

Just found this thread, I'm wondering if you solved this problem -- I think I have the same exact issue -- prior to this I search the thread under "wheezy," and "nasal," but I think "hissing" is about right, too. It is a noise that happens when you press the gas, more noticeable at low rpms, because at high revs the engine and supercharger drown it out. And I also noticed too that I only hear it while the car is in gear, not when revving it in neutral. I think everything on my car is stock. 2005 MCS manual with 67,000 miles.

I noticed a hiss when driving at higher speeds. It's a really low hiss like starting a record or speakers turned up with no audio playing.

BUMP

ive got the same issue coming out of the passenger side of the car.

sounds exactly like this video, a constant hissing/sucking noise coming out of the passenger side

any ideas?

Plugged cat? Someone described having a whooshing sound on a dyno at higher rpms.

Its not that. It sounds like the car is constantly sucking in air. The sound is present even when idling.

Passenger side? The post-sc vacuum line may have blown off somehow? Age + boost? But I feel like that would throw a CEL since that line (correct me if I'm wrong) goes to the fuel pump regulator. Always present indicates a vacuum leak...but I feel like a vacuum leak would throw a code...puzzling.

The cars an 05 S and it doesnt feel like its lost any power. The sound is most present around the oil dip stick and the part of the supercharger that connects to the intercooler.
This sound didnt start occuring until i went through some deep water this past week. Im going to try to get under the car tomorrow or monday

Intercooler boots all good and sealed tight ? not sure if that would cause a hiss but just a thought.

Do you have a boost gauge? If not you should hook up a cheap one and see if you've got any boost loss.

Hi all,

I have a similar problem with my JCW. I am living in Germany and he is a 2008 R56 JCW. 3 weeks ago i had the timing chain tensioner replacement and water pump replacement (i had the exact same problems with my old English MCS and JCW before i emigrated) so i got the fix literally the week my euro garantie ran out....

The other day as i was driving into work i had the 1-2 seconds hesitation/powerloss issue when i was accelerating in 4th gear around 80/90kmh. My heart sunk and i had the dreaded flashbacks of this happening on my english MCS. Back then the problem was much worse and basically killed the car in the end.

This time i have had no CEL lights. My car starts good...no more chain rattle....idles fine and everything feels and sounds good until i accelerate hard....the hesitation has been replaced my a wierd hissing noise when i accelerate hard 3/4/5 gear. The noise is like the interior fans are turned on full and as soon as i lift off the accelerator...the noise stops. I've never had this noise before.

After scouring the forums i think maybe i've got a carbon/oil gunk build up problem that all our DI engines suffer and i was considering doing a water decoke to see if that helped as it feels like the engine is choked or starved of oxygen.

My question is after all that....does anyone have an idea of what my problem is or has anyone else got or had a similar problem?

I know this is the R50/R53 forum so sorry if i am boring you with R56 issues :P

Thanx guys......

Possibly a BOV issue on the R56.... But for the SC editions I would think throttle body at a weird stuck position or the BPV same style of issue.

Wow....I started this thread in 2007. BTW the source of the hissing sound was never established.

Thanks for the advise, Ill check my BOV and the BVP tomorrow. I'm going to do the water decoke through my PCV also but i don't think this will fix my problem....its very strange

@ CHKMINI ...ha! Yes i noticed you had started this in 07, but its the only thread i could find which had a similar 'hissing' problem to mine. :P

I swear to god...if my girlfriend had been as high maintenance as my mini's have been over the years i'd have become a monk!

Did the hissing ever go away on yours ??