5.9L Hissing noise?

Luke(MI) · Jul 18, 2011

It's not the manifold, but it sounds like it's coming from the passenger side of the engine. Constant hiss, starts right away, stops when the motor s shut down. could the alternator bearings be dry? It sounds like it's comming from the idler pulley but I checked the pulley and coated it with pb blaster and it still does it. Also seems sightly under powered, Am I sucking air somewhere? it's not a pat pat pat sound like the manifold would, just a constant steady hiss like a leaky coupler on an air compressor.

pavester · Jul 18, 2011

you checked the motor for any snakes hidden up in there? lol. but for real, you might want to check all the hoses for cracks/dried up hoses

Luke(MI) · Jul 18, 2011

Be roasted snakes lol. will do, I hope it's just minor,

Luke(MI) · Jul 18, 2011

Could it be something with the idler?

nim81 · Jul 18, 2011

Take the belt off to check all the pulley bearings. Check your plenum for leaks. I had a cold air intake on my 5.9l and it hissed pretty loud...

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nussdawg395 · Jul 18, 2011

Could it even be a vacuum leak?

ktm1217 · Jul 18, 2011

What about that gasket between the throttle body and the air box?? I know my truck gives off a little hiss when that gaskets not seated right in there...

txbass06 · Jul 18, 2011

Can you hear it under the hood or just from inside the cab?
If you can hear it under the hood, try pushing down on the top of the filter housing and see if it changes. And check the clamp that holds it down and make sure it's seated to the tb all the way around. I had hell getting mine to seat correctly when I changed my air filter and had to double up on the air cleaner gasket to get it right

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Luke(MI) · Jul 18, 2011

txbass06 said:
Can you hear it under the hood or just from inside the cab?
If you can hear it under the hood, try pushing down on the top of the filter housing and see if it changes. And check the clamp that holds it down and make sure it's seated to the tb all the way around. I had hell getting mine to seat correctly when I changed my air filter and had to double up on the air cleaner gasket to get it right

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Can hear it every where, gets louder on the passenger side.

I will check all of these thanks

ktm1217 · Jul 18, 2011

txbass06 said:
Can you hear it under the hood or just from inside the cab?
If you can hear it under the hood, try pushing down on the top of the filter housing and see if it changes. And check the clamp that holds it down and make sure it's seated to the tb all the way around. I had hell getting mine to seat correctly when I changed my air filter and had to double up on the air cleaner gasket to get it right

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Yeah i know exactly what you mean. I cleaned my filter just the other day and it literally took me a good 10-15 mins to get that damn gasket and clamp just right. I had it aprt a while ago and didnt have it back together right and i had that whistling/hissing noise..bothered the crap out of me til i fixed it. I hate it when my truck makes noises and rattles. Luckily the only thing that really makes noise now is my exhaust rattling and thats only sometimes lol

Luke(MI) · Jul 24, 2011

oil in the throttle body...well, there goes my HID's

Luke(MI) · Jul 25, 2011

how hard is this gasket to change? And is it a special material? I peened most of the gaskets for my Allis Chalmers WD45 tractor and they're holding up so far, could it be done here?

willyjr · Aug 22, 2011

Luke(MI) said:
oil in the throttle body...well, there goes my HID's

Why is that? What's that indicative of? I'm curious.

Mine has done the same thing since I changed the intake gasket a couple weeks ago, but only under load when ready to shift. It drove me nuts :killer:

I was convinced it was a vacuum leak or some such but ended up being a squealing belt.

nim81 · Aug 22, 2011

willyjr said:
Why is that? What's that indicative of? I'm curious.

It means the intake manifold gasket is leaking oil into the intake

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willyjr · Aug 22, 2011

nim81 said:
It means the intake manifold gasket is leaking oil into the intake

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Ok, thanks.

nim81 · Aug 22, 2011

opps sorry i was at work and got ahead of my self it means the plenum gasket is leaking, not the intake manifold gasket. but you have to replace the intake manifold gasket when you replace the plenum gasket as you have to take the intake manifold off the engine.

5.9L Hissing noise?

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