hey guys... i dont ask many questions here, but i have one
to ask right now......
Im hearing a loud hissing sound when im racing my car...
but the sound only appears when i go over bumps in the road...
i.e.: green light, going thru first pulling hard, slam second gear and still pulling hard, when i hit a bump or ripple in the road i hear the sound for a split second, like when the wheel is spinning in the air
before the tires lock back up with the road after going over the bump.....
i dont hear the sound every day during normal driving, only when going thru the gears hard!
I only have two ideas as to what this could be.....


1. I have a leak somewhere in my exhaust near the headers and
cat connection.
2. Its just the sound of the wheel spinning faster because its
in the air not connected to the road.


i welcome all ideas and suggestions

 

You should not be getting enough wheel hop to spin the wheel enough to hear. Perhaps intake noise, mystery to me

 

check where your downpipe connects to your cat. I've heard this happening before if there's enough power, the air will force its way out the gap between the two (because of the springy bolts)

 

intake noise could be it.

You would know if it was exhaust because it wouldnt be like a hissing. It would make your exhaust sound as if you dont have one.

Maybe you have a small leak in a hose somewhere and it puts enough force on it when you are on it hard that you hear it then.

Or you could be hearing alternator whine through your stereo. That can sound like a hissing. If it is from your stereo go and check the ground connection on your amp and your head unit. I think this may be it since it is when you are onit hard and when you hit a bump. A loose ground connection will do that.

 

Ive had that happen header bolts where it goes to the rest of the exhaust needed tightening.

 

Could it be your brakes or rotors???? Just a thought because i used to hear that kind of noise on the freeway whenever i passed over a bump or dip. Moreover i agree with everyone else that it might be one of the bolts from the headers or exhaust need to be tightened. Goodluck man!!!

 

all of your suggestions are very possible....
im gonna put the car up on jk stands in a few
minutes to see whats cookin under there... one more
bit of info... last night, after a cold start, i heard what
sounded like my heat shield rattling...it was a constant
noise for the first 30 seconds the car was running..then
went away and i could only get the sound to come back
by tapping the gas pedal...
so this could be it..... but ill be checkin everything else
that was mention in this thread...
thx for your time and help!
much appreciated

 

looks like the bolt and nut holding the header to the exhaust
has rusted out and become disconnected....from what i can see its only on one side...... do you guys think i should worry about it...beings my wife is going to be driving it for about 100 miles tomorrow????
where can i pick up the proper hardware to make the fix myself tomorrow?????
thx again