Hissing

snarkee · February 2, 2011

took my dash apart as well as removing the guage cluster.....noise still there......if i touch the gas softly and raise the rpm's 2-300 it has a slight whsitle....but when i took it for a test drive it sounds like excess engine noise from behind the dash

bud4ya · February 2, 2011

I am gett9ng the same hissing noise and noticed it today. I was told it was the aftermarket amps etc trying to keep up with the voltage. I will test it tomorrow with the radio off and update.

toothpick · February 2, 2011

I am gett9ng the same hissing noise and noticed it today. I was told it was the aftermarket amps etc trying to keep up with the voltage. I will test it tomorrow with the radio off and update.

I've got no add-ons whatsoever, it's not really a electronic noise I'm hearing. It almost equates to the sound you hear when the road is wet and you get that noise from the tires. Except, it's not there all the time. I've heard and seen suggestions that it may have something to do with the Fuel Trims. IDK though, especially on a truck that doesn't have a custom tune or something similar.

Snow White · February 8, 2011

my truck has done this since day one and i think it has to do with the intake system or the exhaust system/manifolds/resonators.... it's definitely something engine related maybe vacuum related or something like that. it is very noticeable when you're "on it" even with my muffler delete i can hear it.

snarkee · February 9, 2011

well i towed an enclosed trailer with 2 sleds inside and the truck pulled it no problem.....but with the increased load, my hissing was more of excess engine noise coming from from under the dash.....kinda like the excess road noise i get from the back rear crew cab vent lol

ChevyTech77 · February 9, 2011

Air leak around the steering shaft pass through boot?

snarkee · February 9, 2011

thats what i was going to check next....areas around the firewall

ChevyTech77 · February 9, 2011

Block off the cab vents, with some masking tape, start the engine and put the hvac blower on high. Spray soapy water around the bulkhead and locate your leak.

Maybe a fuel line grounding out on the bulkhead too. Seen that a few times.

snarkee · February 9, 2011

Block off the cab vents, with some masking tape, start the engine and put the hvac blower on high. Spray soapy water around the bulkhead and locate your leak.

Maybe a fuel line grounding out on the bulkhead too. Seen that a few times.

will try thanks for the tips

Autonut · February 9, 2011

I got this noise this morning when I started my truck. It came and went with the RPM of engine. It seamed to come from the underside of the drivers side dash. I thought it was because of the cold temp outside. I was about -17c. I have 10800 KLM's or 6700 miles on my truck. If I get it again I'll take it back to my dealer and have them look at it.

Autonut

Rob1 · February 9, 2011

I got this noise this morning when I started my truck. It came and went with the RPM of engine. It seamed to come from the underside of the drivers side dash. I thought it was because of the cold temp outside. I was about -17c. I have 10800 KLM's or 6700 miles on my truck. If I get it again I'll take it back to my dealer and have them look at it.

Autonut

I've noticed this as well....2008 SLT - 55K Kms. It seems to be less noticeable for me in colder weather and more (loader) when it's warmer.

I describe the sound along the lines of a dog whistle or high pitch....does that seem like what you are hearing?

I reported it to the dealer on test drive - the shop foreman hear it and said he would send the issue to GM Engineering. I took this as " I don't know what the issue is and don't care".

Still have not heard back.

If anyone does find the source - please share!!! This drives me nuts sometimes.

BTW - it's not the Radio or climate control - with all off still there.

Cheers

dataspng · February 9, 2011

Wonder if it has to do with factory skid plates reflecting noise back up? Does everyone have the Z package? If so it could be really hard to figure out with the sound bouncing all around.

Had another brand rig awhile back and it had simular noise under heavy throttle and it ended up being the fuel lines making noise with all the gas flowing through it (at a high rate) and the filter bolted right to the firewall under the brake booster. Solution was a rubber washer on the fuel line brackets to isolate them from the firewall.

Just a SWAG I thought I would throw over the wall.