Strange hum/whine/moan coming from intake manifold

[ret]

Well, I've got a noise that has me stumped. I'll start at the beginning here. I got this car a couple years ago, after I had owned it for 6 months or so it started making this sorta whine (not quite a whine, sounds like 1 solid toot of a train horn, but much much much quieter). At some point it stopped, unforunately I don't remember when. Then about 1 year ago I got a new engine (SHO Shop longblock), just this morning, it started making this same sorta whine/moan sound. I decided to figure out wtf is doing this since I'm trying to get it into proper running condition before I do any performance mods (not to mention it's annoying). So I pop the hood with the engine running and listen for it, it's louder in some places than others, the 2 loudest being back by the passenger door and the other up by the air intake. I popped the top of the air intake and the sound got considerably louder, so I angled the air intake up at me, and the sound was definitely coming from somewhere inside, beyond the intake. I should note that friday I got the egr valves in the intake manifold cleaned, which is the only change that has happened recently. Also, it seems to go away when I turn on the a/c (a/c pump doing something odd maybe?). Anyone have any idea what this is?

EDIT: I should add that when I hit the throttle, the whine goes away until a second or two after I let off the throttle.

EDT #2: I found it quits making that noise if I turn anything climate control related on. It's not just a/c. If I turn it on so it blows hot air, defrosts the windshield, etc it will quit making that noise.

<small>[ April 15, 2002, 08:24 PM: Message edited by: ret ]</small>

 

[93SHOCOOL]

I am no expert or anything, but I am having the same problem. I think it might be the valves. How many miles have you put on the new motor?? If it exceeds 60k I would highy reccomend doing a 60k service on it.

 

[ret]

I've only got about 25k on the "new" motor, so that shouldn't be it, but who knows... It's also clicking as if the valve gaps may be screwed, so I wouldn't be surprised. I'm going to run engine flush through tonight and change the oil, hopefully the click is a sticky lifter and this will fix that.

I'm not sure about this horn sound though... I wonder if maybe when the climate control is off something doesn't seal up quite right and it's doing sort of like when you blow across the top of a bottle, and when the climate control is on, something opens up that changes the air pressure and corrects it.

Anyone else run across this? I'm a bit scared to drive my car with it being like this, but I have no choice, so I need to fix it asap if it's doing any damage.

 

[1slickRED89]

"Anyone else run across this?"

my car does that just after the first start of the day, for about 2 min. also when the a/c cycles. with a K&n filter you can here it very clearly in the drivers seat. i would like to know what it is for myself, but i have bigger fish to cook.

Corey
89SHO

 

[ret]

Well, at least it sounds like my engine probably isn't getting ready to blow up on me.
**Waits for sdpatt's usually correct answer** wink