MarineBlue03GMC

Since I installed my ASM headers I think I am hearing a new sound my engine never made BUT I am not really sure.

The sound is like a quiet hiss of air when accelerating, almost like the sound of a small turbocharger under boost?!

My truck doesnt feel like it has lost any power and I recently dynoed my truck and the power seemed good. I have thoroughly checked under the hood ALL around the header flanges, downpipes, exhaust pipes, etc. and have found NO signs of header/exhaust leakage. These facts would lead me to believe that there is NO leakage.

Now I was looking for some black soot or carbon deposits around the header flanges. Is this how I would spot a exhaust header leak?

I have had exhaust leaks on other cars before and my trucks hissing noise doesnt sound like a leak. Does anyone know what this sound could be?


Could it be from my UPD intake system not being installed perfectly? I had to remove my UPD to install the headers so maybe its this?

What would a small header leak sound like?

This has become real annoying and I am curious whats up, if anything with my truck! It only does it when accelerating.

Ryan23silverado

iTrader: (1)

Have you retourqued the header bolts? You should do this three times after each time bringing the engine up to temp and holding it there for a while. A leak would sound like a really annoying hissing/ticking sound. It is a pain, but to tell for sure if you have a header leak loosen the header and take out the header gasket. Any black marks outside of the exhaust port shape would mean it was leaking. Good luck

MarineBlue03GMC

I havent retorqued the bolts but I put in thread lock so they shouldnt back out should they?

BUT it does sound like an annoying hissing sound! What a pain in the ***! I hope I dont have to completely remove the headers!

I guess I will check the bolts and retighten them if needed. What were the torque specs on those again?

If I retighten them and I still hear the leak should I pull of the gasket and then check for signs of carbon/soot and leakage?

Hit Man X

I too use threadlock on header bolts, I did it once. Let them setup overnight before I drove the truck and all was well for over a year. I doubt you have a flange leak. A header leak would be LOUD and exhaust would be getting in the cab...not good. A loud tick like a bad lifter sorta.

Get a thing a doctor uses to check you heart (stethescope?) without the cold round part and use that to put by the collectors and stuff. That will amplify any leaks so you can hear.

I'd also try reving up the truck and listening for leaks and using the back of your hand to feel for air leaks.

Check for intake leaks first. Begin with the most simple stuff.

Is it like a ticking sound? I could just be your EGR too...?

MarineBlue03GMC

Maybe there isnt an exhuast leak beacause it definitely isnt loud.

I will try the stethoscope method.

The sound is definitely not a clicking sound either.

Its DEFINITELY a "sssssssssss" sound. What the hell could it be? At idle I can hear "ssssss" sound but it seems to get louder when accelerating. So maybe its this same sound during idle? I just dont think I remember hearing this sound BEFORE my header install.

It actually sounds like an air vacum sound!? SO maybe it is the intake!

BlownChevy

iTrader: (20)

Hey Glenn, I have a stethoscope if you want to borrow it.

JWRENCH

The headers just naturally have a rushing sound to them and make more noise under the hood too so it may just be that.

hodgeee

Usually in my experience it is the header to y-pipe flange that makes that noise. I had the same leak, then I extra torqued those bolts and my hiss went away. The gaskets that they use for a flat flange to a flat flange suck. I like the ball and collector type of conection, and have never heard one of those leak!

MarineBlue03GMC

Yea I had all the pipes welded and setup at a muffler shop. I recently went back to the muffler shop after I starting hearing that sound and the shop didnt find ANY leaks under the truck. SO its either an exhaust or intake leak or some other possibly "natural" sound.

I am going to take blownchevy up on his offer to loan me a stethoscope to check for air/noises.

Hit Man X

I'd check out your intake system first...it probably is okay. I am not sure how the UPD works as I have never seen one in person, heard one, or driven a vehicle with one.

I'll give you a "for instance" story...when I pulled my stock intake off my F-150 and put a K&N FIPK on with a ported MAF it is pretty damn loud now under the hood with that sucking sound of the intake. It is like putting a vac hose to your ear. Very loud! I basically went from a slit of 2" x 5" on the intake box to a 2.75" gaping hole with a huge cone filter.

Here are some pics of the "other" truck.

http://www.ford-trucks.com/user_gall...p;albumid=4253