Whistle or Squeal when hood is down

[jkendall86]

I have a strange problem. I have been chasing it for a while. When my engine is edling, or when I am driving and decelerate and the rpm's go to below 1500, I have a whistle or squeal from the engine bay. It sounds like it is from around the power brake fluid reservoir. The funny part is, when I open the hood to look for it, it goes away. I played with it a bit today and if the hood is down it makes the sound, if I "pop" the hood I have the sound, but if I raise the front about 3 inches, it goes away within about 2 seconds. What the heck is going on?:1zhelp:

Have investigated more...it does not do it when cold. I still have the sound when reving in park or neutral, past the 1500 mark. I have the sound when holding the speed steady, but not on acceleration. I was able to raise the hood and have the noise remain. I put my ear to the air intake chamber and that is where it seems to be coming from.

 

[robeats91t]

Does the whistle go WOO WOO?

*ducks*

Does it do it cold, warm or both? And seriously, how loud of a whistle is it?

-If it's coming from around the power brake booster area, check for cracked vacuum hoses coming from the intake mani to the brake booster. Also, make sure the check valve is not leaking. Maybe check the brake booster too to make sure it still holds vacuum.

-Have you changed/replaced anything on that side of the engine lately? Is the egr valve in place and working properly?

Just a few thoughts. Good luck with the troubleshooting!

 

[jkendall86]

The whistle is pretty loud...I can't isolate it because it goes away when the hood opens. I have about 3 seconds before the sound stops. I havn't replaced anything and the hoses seem to be ok....I am really curious about the reason it would do it when the hood is down and not when it is up....

 

[JASONA70]

lift the hood, give it some throttle and check ^^ probably something is up around where the belts are.

 

[jkendall86]

Its not from the belts. When I stand by the drivers side fender, it is coming from up by the windshield. It goes away when I put the hood up...but if the hood is down and I put it in park, the noise is still there when I rev it up, when in drive it goes away when I rev it up.

 

[JASONA70]

:aigo: thats really really weird... check if its a engine or etc items.

 

[mrnickleye]

Just a thought.....Our engine bays are very packed, and air has a problem getting out. The cooling fan may be trying to force air out of the engine bay. The rubber seal for the hood at the firewall may be leaking a little and cause the whistle.

I removed my seal to allow more air flow out of the bay. It does help keep the engine cooler, as more air can pass thru the radiator.

 

[jkendall86]

The sound stays for about 3-4 seconds after the hood is open. I opened the hood quickly to see if I could hear the sound, it was there long enough for me to know that it is up near the brake reservoir. I also thought of the seals making the noise. It is really strange.

 

[mrnickleye]

There's vacuum lines to the cruise control servo. And along firewall over to the heater control valve.

There's exhaust pressure on the back of the head at the EGR cooler cover. And at the tubing to the EGR valve.

Intake manifold vacuum leak can give whistles.

 

[jkendall86]

Any ideas on how to track down where it is coming from since the hood has to be down to hear the noise?

 

[7mMk3Pimpin]

try putting the carin the air on jackstands and have someone drive the car at the points where it makes the noise while you look underthe hood.. hope it helps

 

[tookwik4u89]

Any ideas on how to track down where it is coming from since the hood has to be down to hear the noise?

Does it idle right? If its a vac leak you can find it by spraying carb clean around and rpms will jump if you spray it at a leak.

 

[jkendall86]

Last summer I replaced most of the vacuum lines with silicon. I zip tied all the lines on. I also replaced most of the stock tie pressure connectors with screw on type. The vacuum line to the intake from the brakes is a good place to start, don't know if the connectors were replaced there or not.