Update on hissing noise Re: Header -New gaskets, no change

New edit: See bottom of post


SCROLL DOWN FOR NEW VIDEOS - Please listen to the background hissing noise and swing me your diagnosis below

2002 Accord SE sedan 4 cyl (f23a1)


PROBLEM:

Hey guys, I recently installed a 4-2-1 Megan stainless steel header with new flex pipe and immediately after I discovered a very annoying, ugly noise.. so I've looked at my ride a couple of times on the hoist trying to locate it..

When accelerating, and the engine is under a load I'm getting a very strange high pitched "hissing/pissing" noise.. Sounds like it's coming from under the vehicle. It's barely noticeable when the car is not in gear and the engine is revved. I'm sure its not a exhaust gas leak at the gaskets, or where the flex pipe and pre-cat join.. However that's exactly what it sounds like (an exhaust leak).
I re-tightened all the bolts at the exhaust flanges while feeling for a leak with a friend holding the gas pedal with no luck and I also tightened the extra O2 sensor plug bolt... It seemed to help for a few km, but eventually the noise came back as loud as it was before.. (yes the manifold is torqued to spec)

So I was thinking it could be because the rest of my exhaust system is stock... the gas is coming out of the CC faster, but being slowed by the stock restriction in the pre-cat and cat? Any ideas..? Perhaps the gaskets are just of poor quality and the gas is finding path of least resistance? (They are all paper-type/cardboard that came with the header and very slightly damaged during shipping...) I was thinking about getting all new metal gaskets, but I assume it wouldn't be easy to find one that fits the lower portion of the header (before flew pipe)..

It's very hard to simulate the noise to full effect in a garage while looking for the source of the noise... Even on a dyno it wouldn't be that noticeable...

I'm going CRAZY and just looking for some ideas/answers... I can upload a video with the sound later today...
and yes.. I've friggin searched, more than a couple occasions


VIDEOS

Under the hood

Me Driving


UPDATE: JULY 6 '11

So i found out that there is a metal crush gasket that connects the flex pipe to the pre-cat. Thought this would solve my worries as the sound got worse and worse. Also picked up a new manifold gasket (stock 2 peice metal gasket) and some permatex.


Nothing worked! Sounds a lot better, but still very noticeable! I took everything apart, found that the gasket joining the header to the flex pipe was destroyed in the corner about 3 inches wide.. tossed this and just used permatex. I also put it on both sides of the pre-cat connection.. along with the crush gasket

My buddy from work was working on his civic si beside me and came over to check it out... He told me he also had the same problem installing a header on his friend's civic.. with remainder stock exhaust. He said he also checked all over for leaks, got new gaskets and hardware.. but still the noise persists. He thinks the problem is because the rest of the exhaust system is stock.

Also, this guy is a licensed mechanic civilian side before joining the military as a vehicle tech, just fyi (as am I, soon to be qualified)..

SO! Agree with my buddy? I do and i don't, only because i've read other people's posts and some have installed just a header/flex with the rest stock with no noise....

Re: Strange hissing sound after installing header

Either you purchased a bad header with a leak or it's the gaskets. From what I've heard, Megan makes terrible gaskets that leak all the time.

Re: Strange hissing sound after installing header

1. did u torque the bolts down correctly?
2. did u bolt it down using the correct pattern?
3. and yes, their gaskets suck

Re: Strange hissing sound after installing header

DarkSideAccord said:

1. did u torque the bolts down correctly?
2. did u bolt it down using the correct pattern?
3. and yes, their gaskets suck

Click to expand...

1:

SuperMidget said:

"It seemed to help for a few km, but eventually the noise came back as loud as it was before.. (yes the manifold is torqued to spec)"

Click to expand...

2:
Yes i used the right pattern, inside to out. I even step torqued them.


3:
Where can i get a good gasket for the header to flex pipe connection? its a 2 barrel flange.. Or what material can i make one (?) in?

Re: Strange hissing sound after installing header

jwong512 said:

Either you purchased a bad header with a leak or it's the gaskets. From what I've heard, Megan makes terrible gaskets that leak all the time.

Click to expand...

This makes sense... i can see the gas leaking out under high flow periods through a pin size hole, making the type of noise my car does.. cool...

I originally thought that the clamping force of the bolts would more than suffice the sealing needs for the gas... there's not a lot of pressure in the exhaust system... right?

Re: Strange hissing sound after installing header

I get the same wierd noise. Except I have a bit of a rattle too. I never had a rattle before I gutted the cat. Buy I havent had the chance to check all the bolts ect. I know I probably have an exhaust leak where my dcheaders meet together.

Re: Strange hissing sound after installing header

Well, I have a DC Sports Header and I remember calling them asking where I can get the gaskets. They gave me the part numbers of the Honda Gaskets I could use in there. They weren't the ones made for our cars but they were a perfect fit. Maybe you could call Megan and have them do the same?

Re: Strange hissing sound after installing header

my ebay header's used to hiss. i just ignored it since it was a very slight hiss. sometimes I just pretended I was boosted.

Re: Strange hissing sound after installing header

hahaha thats what I pretend!

i'm gonna get new gaskets, already got a guy looking for them..

He said that the manifold gasket that came with it (paperlike material) is squish-able to ensure a good seal to the exhaust. And he said if the two mating surfaces aren't perfectly flat, it wont seal with the stock gasket (2 piece THIN metal gaskets).

I'm gonna try to swap out the other 2 gaskets downstream of the manifold, but like i said, i've been having a problem finding the gasket that mates the header to the flex pipe. (2 barrel, 3 bolt hole gasket)

Just gonna try stock exhaust gasket for the flexpipe to pre-cat connection. Hopefully the metallic material will fix the problem...

Process of elimination!
Thanks for input... any more is muchly welcomed

Re: Strange hissing sound after installing header

SuperMidget said:

hahaha thats what I pretend!

i'm gonna get new gaskets, already got a guy looking for them..

He said that the manifold gasket that came with it (paperlike material) is squish-able to ensure a good seal to the exhaust. And he said if the two mating surfaces aren't perfectly flat, it wont seal with the stock gasket (2 piece THIN metal gaskets).

I'm gonna try to swap out the other 2 gaskets downstream of the manifold, but like i said, i've been having a problem finding the gasket that mates the header to the flex pipe. (2 barrel, 3 bolt hole gasket)

Just gonna try stock exhaust gasket for the flexpipe to pre-cat connection. Hopefully the metallic material will fix the problem...

Process of elimination!
Thanks for input... any more is muchly welcomed

Click to expand...

When I installed my DC Header (that was a nightmare), I used an OEM Honda gasket for the header itself. Way better quality than the cheap paper autoparts/eBay gaskets. As for the flex pipe to header, I used Permatex Ultra Copper gasket maker. It's about $7 plus tax at any auto parts store and can withstand heat up to 700°F or 371°C. Stuff works good. I also bought the OEM flex pipe to cat gasket as well. It's a metal ring that crushes to the wall of the cat/flex pipe to seal the two pieces of piping together. I applied Ultra Copper on this surface before adding the metal ring on the flex pipe to cat area. No leaks or loud noises. All for about $14 for the gasket sealer and metal ring crush gasket. No pre-made gasket is required for the header to flex pipe. Just use Permatex.