Roaring noise from engine compartment

[John G]

Intermittently, when I start the engine, while still in park, there will be a steady loud tone coming from the engine compartment. The tone is a sort of flute-like sound, like blowing air across a coke bottle, except much louder. The sound is not warbling or modulated, but is steady in its loudness.



With the hood open I am unable to pinpoint the source, but it seems to be loudest when I stand near the passenger-side headlight.



The occurs about one time out of ten that I start the engine. If I turn the engine off and restart it usually goes away.



Any ideas?

 

[Ed Fenwick]

Noheat, is the sound when the engine is cold, hot, both? Could be a vaccum hose but they are higher pitch and the engine will run rough. Check to see if there is anything near the fan. Check the air cleaner for tightness. Keep us posted.

Ed

 

[swshawaii]

No guarantee, but the IAC valve should clean.

 

[John G]

The engine does not run rough when this noise occurs, so that might rule out a vacuum leak or IAC valve.



The air filter box suggestion is interesting because it suggests a maintenance-induced-failure, and indeed replacing the air filter is the most recent service I did on the truck. I recall I struggled to maneuver the lid with its attached hose when I did this service, but I think I got the job done, and I don't see anything obviously wrong with it, though, when I inspect it - the two latches are latched and the large diameter hose on top seems to be in place. Is there something else I should look for, with the air filter box?

 

[Yardsale]

I doubt a sticky IAC would cause a noise.



Hot, cold, all the time? Did this begin immediately after the air filter service?

 

[RedRanger 7]

I assume you are mechanically inclined, so try undoing the hose to your filter box and the lid is a lot easier to remove and reinstall. You will also get a better look at your radiator fan and see if it is a little bit hard to spin. You will also see your serp belt a lot easier in case you get the urge to change it yourself one day. :driving:

 

[Jackson Ellis]

To pinpoint a noise under the hood, take a 3 or 4 foot section of garden hose, and hold one end to your ear. Sweep the other end over the engine compartment until you zero in on it. It's especially good for vacuum leaks; you can even pinpoint the difference between two lines that are right next to each other. If the air cleaner box has a leak, then you'll be able to find out exactly where it is. Standard cautionary statement about handling a garden hose with moving parts applies....

 

[John G]

I think my roaring noise might be from the fan clutch. It typically occurs when the truck is started the second time of the day, not the first time, and then it does go away. Afterwards, with the engine stopped, I checked to see if I can turn the fan by hand, and the fan turns easily but it doesn't spin loosely.



So now I'm wondering if this is a normal fan-clutch noise, and I just haven't noticed it before.

 

[Ed Fenwick]

Wife's Jeep does that since the clutch was replaced. After warm up, it goes away. I try to ignore it.

Ed

 

[scott degroot]

In some instances the IAC valves will make a very loud "moan" type noise. Something in the valve goes bad and causes this and usually there are no other symptoms other than the noise. I have tried everything in the past to fix this issue with no luck, a new IAC always cures it though.

 

[John G]

:sad:The idle air controller turned out to be the problem. So swshawaii was right.



I did not know that the IAC could cause a noise, but it did. The previous time my IAC failed I just had problems with stalling at idle in the winter, with no noise. This time three years later it was a roaring sound from the intake area, under the hood, with just some occasional idle problems, and it was summer. IAC both times.



The noise sounded just like the YouTube videos for a bad fan clutch, but that wasn't it.



Maybe I should just buy a spare IAC and keep it in the truck, with a 10 mm wrench. It is not hard to change, and it happens all too often.

 

[Yardsale]

You have bad IAC valve juju.



I have the original IAC at 225,000 miles. I think I've cleaned it three times as a preventative maintenance item (no idle or noise problems).



I clean it with contact cleaner and a Q-Tip and then put a drop of lightweight (3-in-1 or gun) oil on the shaft where it enters the motor and the bushing at the opposite end.