Hissing from exhuast after shut down

[ABlownBlueOval]

2014 GT500 - "mods" in signature

Last night I took the car out for a quick blast. I let it come up to temperature and give it a good flogging. I just got Nitto NT05R's installed so I wanted to see how they handled. (Very impressed with them). Anyway, after a spirited drive I pulled the car back into my garage let it cool down idle for 30 seconds and shut it down. As soon as the engine noise died I heard a loud hissing coming from the right muffler. It was so loud it sounded like someone unscrewed a valve stem, and having just had new tires installed thats what I thought it was. Turns out the hiss was coming from the right muffler and the garage smelled similar to burning plastic. I don't know if it was a cat going bad (car only has ~3700 miles). Two days ago I rinsed the car and put it away wet so I thought maybe it was just water burning off in or around the exhaust, but the chemical/plastic smell has me concerned.

Can anyone give any input as to what the hiss was and/or burning smell?

Thanks,

Keith

 

[BlueAngel2014]

Look under the car around that muffler and see if you hit one of those plastic grocery sacks. They will wrap around your exhaust and stink like hell until you burn or scrape it off.

They can easily get sucked up under the car and stick to the hot exhaust. The hissing you hear may be it frying on the exhaust.

HTH

Mike

 

[BOOCOCKY]

Look under the car around that muffler and see if you hit one of those plastic grocery sacks. They will wrap around your exhaust and stink like hell until you burn or scrape it off.

They can easily get sucked up under the car and stick to the hot exhaust. The hissing you hear may be it frying on the exhaust.

HTH

Mike

I had this exact thing happen to me. It melted around the exhaust and stunk like burnt plastic. I ended up scraping it off, good times.

 

[ABlownBlueOval]

That was what one of my buddies suggested. I looked under the car pretty thoroughly and saw nothing that resembled a plastic bag or melted plastic bag. The car did it (not as loud) again this afternoon after flogging it on the way home from work (2-3 mile drive). Called Ford and one of the service reps said maybe it was the S/C wategate/bypass staying open and bleeding off the pressure inside the charger, but that doesn't really seem logical to me. I don't know. Car is running very healthy, and its still under warranty so I'm not going to worry about it - but still open to any ideas or thoughts?!

 

[biminiLX]

When you say Right muffler do you mean driver or passenger side?
If driver/fuel door side, might be evap release? Probably good to inspect that muffler carefully, could have a very small leak? I'd be crawling under there while its making the noise to check it. Good luck.
-J

 

[Grabber13]

Definitely sounds like the bypass. Mine does the same thing, as did the Whipple on my old '07 (more so after running it harder and building boost). Normal, I believe because I never had any issues....

 

[Tob]

My Whipple hisses upon shutdown for a second or two.