Loud Whistle from inlet manifold area

D

dbcopper

Registered
And I mean LOUD!!! It is steady too, no pulsing or intermittent action at all. I have to wear ear protection just to search for the noise. It began suddenly two days ago on a trip. I drove it on and experienced stumbling and hesitation from the engine at lower RPM's. It ran fine otherwise. Dogs between San Francisco and Grass Valley, California are still yowling. It seems like a vacuum leak. When the engine is turned off, the noise dies slowly over a second or two.

Using a pair of ear protectors with a small tube running from one ear, I listened and isolated the sound to beneath the air inlet tubes and near the second cylinder on the right bank.

I'm thinking that a gasket has given up it's "gasketing" job for the winter. Any ideas or experience with something like this? All comments appreciated before I go deeper into the removal of things that I wish that I didn't have to.
Cheers,
dbcopper
 
sounds like a vac leak. The hole is prolly just the right shape to make the whistle... try disconnecting the vac lines in the area one at a time and see if any of them change the sound. Could be intake tube aswell check that pretty good too.
 
Last edited:
It's definitely a vacuum leak

It's definitely a vacuum leak

I didn't have much doubt that it was a vacuum leak, but none of the usual suspects came to mind ... just tinkin' around is not going to work ... it is so darn loud that you cannot hear any other engine sound. (I'm talking cop car siren loud when you're under the hood) Disconnecting hoses is clearly not going to pinpoint the issue. Wondering if anybody else had something similar happen and located the actual suspect.
 
My LSC made a loud whistle sound then it went away as the leak developed bigger...

Mine was an intake manifold gasket. Nitrous does evil things...
 
Manifold Gasket Leaking

Manifold Gasket Leaking

I will bet that you are right. That seems the most likely culprit ... will post a follow up when it is finally located and repaired. Thanks for the input.
 
I don't know about the sound being that loud, but if it is running rough then its almost an assured EGR system leak. My car ran rough as low rpms and the idle jumped when my EGR valve gave out. Sounded like the car was on a heavy cam.
 
This IS a leak at the intake manifold gasket. Guaranteed. The seal there is so tight and so small that you probably won't be able to see where its broken, but its definitally the gasket. I've seen and heard this many times.
 
Thanks for the tips ... sounds like the inlet manifold is coming off starting today ... any tips or other warnings would be appreciated ... thanks to all who responded!!!
 
Leave the EGR valve attached to the EGR Pipe and just undo the EGR from the manifold. Before you remove everything, take a leaf blower and blow out all the crap around the intake.

If its a 93-96, leave all the wires attached to the coils and just remove them from the spark plugs, saves time.

Leave the fuel injectors/fuel rail ON the intake, just remove the fuel lines with the "special" tool.....make sure you have it before you start.

Also, don't worry about draining the coolant or anything.
 
All good stuff, thanks once more ... I have the manifold loose from the heads and ready to lift off or dynamite into oblivion. too late and cold to continue tonight ... what is the tip regarding the throttle body or otherwise lifting or sliding the manifold up, forward and/or out of there? I see the thin red seals and have no doubt that this is the problem ... seems like a weak link in otherwise well engineered power plant. It appears that the throttle body may be removed and left in the engine bay ... am I missing something? I usually overlook the obvious and the simplest way to do things ... appreciate the comments so far, specially the blower idea ... nothing like the old mow and blow technique for the family hot rod!
 
You can either leave the TB on the intake and unplug the two electrical connectors, or you can just unplug and disconnect the TB.

The easy way would be to take of the wiper blades and remove the plastic cowling on the firewall. This will make it so you can lift it right off.
 
what's the trick with the exhaust gas tube under the rear of the manifold ... is that a nightmare or am I missing the quick way to get at that item? I cannot even see the connection point let alone get a tool near it ... I'd appreciate any helpful comments from anybody following this thread ... ran out of hair scratching my head over this one!
 
You use a 10mm socket (or 8mm?) and just remove the EGR valve from the throttle body like I explained above. Leave the "gas tube" ATTACHED and don't try to remove it. Hope I'm not too late.
 
You must log in or register to reply here.
Back
Top