OK guys, after I installed HS Headers(about 1 year ago) I had everything tight and had no air leaks and NO I didn't change the gaskets . Well, now as soon as I start my car up in the morning the engine bay has a somewhat loud hiss to it for about 12 seconds and then stops. It almost sounds like when it stops it is being sealed. Now, when the car is running in any gear, giving that the rpm's are high, when I let off the gas pedal I can hear the same hiss again when the rpm's drop from 3000 to 2500, it then goes away again. Do I have to replace the gaskets?
Yes, I have felt around for leaks myself and have taken it to a muffler shop twice and they have found nothing.

 

Are there any pin holes possibly in any of the welds around the flange?

 

I looked everything over and didn't see any defects.

 

Uh oh Harm buddy.....

 

You could fool the ricers into thinking you had a turbo....

I would imagine that you have a small leak somewhere that is being sealed up when the metal heats up and expands. You'll probably have to rip it out and put in new gaskets. It's a PITA, but that's what you'll have to do to fix it.

 

try checking between the y pipe portion of the headers and the cat/testpipe. if your hotshot flanges are like mine, they are fairly thin. both my old cattman y and stock y pipe flanges were much thicker. if the leak is large enough like mine then you should be able to feel it. you can try picking a new gasket from nissan and using high temp rtv silicone by permatex. i have gone this route and it helps for a while but always seems to come back.

 

I have no problem changing the gaskets, even though I would rather not, but doesn't auto zone carry gaskets for our headers? How much are they anyway?

 

...and yes Foobeca it sounds like a shi!!y a$$ blow-off valve

 

i am not sure if autozone has them or not. i typically just pick up the oem metal gaskets from the dealer. i pay about 5 bucks a piece.

 

Oh that's it!! I thought they would be like 30-40 bucks

 

....back in the day hot shot headers used to like to crack on the sentras.....hopefully it is just a gasket...and yes you can get them at nissan for cheap

 

aawwwww.....your car made good power too

 

I have the same issue....however I need to change my gasket between the Y section and the main cat

 

BTW, how do you like the power the headers gives you? Are you happy or disappointed with the power gains? Was it worth it?

 

Absolutely! I am more happy with what the S-AFCII has done, but the headers were still worth it even though they were more expensive. I am working on getting my stereo system put in now.

 

33whp, I love them

 

Make sure its not your flex pipe that is making the leaking/buzzing noise. I have self locking nuts that have been torqued down in sequence (like the FSM says) on the head/header flanges. I have reused my old exhaust manifold gaskets and they do not leak. The Ypipe section is also using self locking nuts with HS supplied gaskets and I have yet to have any leaks. I've had the headers on for almost a year now (10 months) and they still look like new and I have isolated every leak and the little noise that sounds almost like the bees in the can some Ypipes have - is still there, but thats due to the flex pipe, and it doesn't bug me at all.

 

Why would you need a S-AFCII unless you are FI or juiced with larger fuel injectors?

 

there are some vq35s with bad AFRs due to bolt-ons....harmbone gained some nice #s with the s-afcII

 

Thanks for the info guys. I am going to thoroughly check it out next weekend. If I find anything worth mentioning, I will let you guys know.

 

I was under the impression those gasket do not need to be changed since they were metal gaskets? Well i didn't change mine and i really don't plan on it now. I'll just let the supercharger noise drown out the noise