hissing sound

[Linebckr49]

so today driving the car i noticed a nice hissing sound coming fromt the engine. the hissing increases as rpms increase. i thought, "damn, someone musta slapped some turbos on my car during the night!" so ya, my NA now sounds like i'm building boost as i accelerate. so i've got this hissing sound...but i don't really wanna get rid of it....haha.

well its coming from the drivers side, so around the belts & pulleys side of the motor. sound occurs with the A/C off (haven't tried turning the A/C on yet to see if it makes a difference).

--i'm guessing a belt? but i changed my accessory belts 20K miles ago when i did the 60K service. but let's not rule out a squealing belt just yet.

--could it it be a pulley on its last leg?

i'm busy hacking up headlights to do the HID retro-fit right now, so i don't wanna go fishing for this problem just yet. a friend of mine mentioned a possible vac hose leak/disconnected. plausible, but there are no hoses on that side of the motor.

any other ideas?

[Igovert500]

lose vacuum hose was my first guess.

Have you had the plenum off recently. Perhaps the gasket is leaking?

[VR43000GT]

Yeah, I think Linbckr was the one who had his plenum powder coated right? Otherwise it does sound like an air leak somewhere seeing as how it sounds like a turbo.


Now all you need to get is one of those fake BOV sounds that come from the engine. lol

[Linebckr49]

hmm. i DO have a plenum spacer. perhaps i'll see if the bolts are loose and check the gaskets while i'm in there.

[Linebckr49]

Originally Posted by SL3000gt

Yeah, I think Linbckr was the one who had his plenum powder coated right?

no, i got my front valve cover powdercoated. but i haven't installed it yet. waiting on the valve cover gasket.

but ya, i hope its a leak rather than a belt/pulley.

[VR43000GT]

Ah crap, I had to look it up to be sure. I was certain I remembered you having the penum done. First thing to go is the mind........DAMN, I'm only 18, I'll be senile at 30.

[AutostradaVR4]

hmm...have you tried just listening around under the hood while someone tachs it up? I would think it shouldnt be too hard to isolate the sound.

About that plenum spacer, how'd that work out for you? Im looking into one...but i heard someone say they had hood clearance problems.

good luck man

[Igovert500]

Linebckr would obviously know from experience. However, I was under the impression, that they really aren't all that great for performance on FI cars. Carbuerated they help more. However, obviously the spacer does reduce plenum temps, which technically isn't a bad thing.

[Linebckr49]

Igovert is right about the plenum spacer. it does help to lower intake temps. and theoretically, since it makes the intake runners (tubes) longer, that should help you reach your max torque output sooner in the RPM band. however, its not a very noticeable difference in performance. more of a psychological thing (since installing it, i think it should help me out, so i'm thinking that it must have improved the performance...but not really).

but yes, on a carbureted engine of a couple hundred cubic inches, the plenum spacers DO help quite a lot. b/c of this in NASCAR and other stock car racing leagues, one of the requirements is a specific size plenum spacer (or something to that effect) that limits the max. hp the engine can put out...to make the competition more even.

--> ya i'll have someone tach it up while i listen. shouldn't be that hard to hear. i just have that godawful lifter tick again so it makes isolating the hiss a bit difficult.

[Linebckr49]

when i turn the A/C on, the hissing (now turned into a squeaking) definitely gets louder.

do you guys think its (a) belt (b) pulley (c) compressor clutch ??? or a combination of those?

ya, i know i could tear her down and check, but i'd rather just work on the HID retro now, garner your opinions, then check it out.

[Ralliart 3000gt]

You might have the same problem as this guy.....

[Igovert500]

I'd check the pulleys and accessory belt.

[TorchedStealth]

I had a squeak on my last engine that i had in my car. It was one of the pulleys (not sure which one though). It sounded like a BOV especially when it shifted in the high rpm's when i really got on it. Its still in my trunk and i actually think it was either the a/c pulley or underdrive pulley. I lubed some of the pulleys with WD-40 that were visible from the top of the engine bay (without getting it on the timing belt of course) And it went away for a while.