2.7 LCE header...hissing noise.

Whats up fellas?

I recently installed an LCE header on my truck and since finishing it I have noticed a subtle hissing noise coming from the header location while driving.

It happens under load only, like under acceleration or revving it in neutral. No hissing at idle. Its a lot easier to hear when the door and windows are closed. When your outside the truck its nearly impossible to pinpoint. I tried having a buddy plug the exhaust with a rag to make the possible leak louder to pinpoint it but that doesn't work.

I replaced the EGR gasket b/c the one that LCE provided seemed a bit cheezy so I replaced it with a felpro gasket. It didn't help....

Any ideas? Is the hissing normal with an LCE header? I had a cracked manifold before installing the LCE header so I know that a usual exhaust leak the far upstream in the exhaust is more like a tick not a hiss....so I am stumped....

ideas?

 

bump...anyone?

 

Try torquing your header bolts down in the right pattern.


then check the flange connection at end to your O2 sensor/cat...tighten it up.


Might came loose if you didn't torque to proper specs.

 

hmmm...i re-torqued everything already, but didn't know there was a specific pattern to tighten the header nuts. I tightened the down by alternating to the right and left side and alternating top and bottom. Whats the specific pattern?

 

bump....anyone else?

I think I am going to order a gasket set from LCE just in case I pinched the header gasket...idk where else the leak/noise could be coming from...

 

I would think that if it was an exhaust leak you would hear it at idle too...

You descibe the noise as a hiss, can you be more specific or maybe make a recording and post it?

I am wondering if is simply the normal sound of headers. The sound coming through the header tubing is a lot different that what you hear from a regular, cast iron manifold.

 

I will try to get a sound clip/video of the outside/inside. I just noticed yesterday that at idle there is a slight tick coming from the header side....but I never got to hear the motor w/o a cracked manifold so I dont know if its just the valve train or what....I might also get another can of seafoam and run it through the truck to pinpoint the leak too...

 

Having similar issue with my truck. Ever figure out what was wrong?

 

Check the EGR tube gasket as well as the Gasket at the Catalytic converter. I have had multiple issues over the years with both of those joints with my LCE long tube header. I ended up using copper rtv and it helps to make the gaskets last longer.

 

11-1/2 years has passed…OP is likely into a different project by now. LOL

 

Looks like the OP hasn't logged in in almost 4 years.

 

Zombie thread dude.

But hissing sounds are often vacuum leaks. And old trucks have rotten hoses