Car engine noise, cause?

[AKS\/\/ulfe]

I just notice it yesterday, in the morning after a thunderstorm that night, that there was a whistling hiss coming from the engine. As I sped up, it went away, the closer to idle the engine got, the louder it became.

Gunning the gas made the noise go away, then it would come back as the engine returned to idle.

Any ideas? "Bend me over and take my cash" mechanics are out of the question.
-SW

[eagl]

The exhaust recovery tube, a thin tube from the vicinity of the first catalytic converter back to the intake, often has a seal that will give out.  My first suspicion is either an intake or exhaust seal problem.  If the sound has any "ticking" element to it, that tends to mean it's an exhaust gasket.

[lazs2]

really difficult to be accurate from such a descritption but it sounds very much like a vacumn leak..

At low (engine) speed you have high vacumn and the noise would be more prominent.. when the motor is under load vacumn drops and the noise is less noticeable.

A vacumn gauge would tell you right away... failing that... start tracing hoses.

lazs

[Casca]

Sounds like it's leaking vacuum.  Find a piece of hose a couple of feet long, you can listen in one end and move the other end around your intake components till you hear it.

[Siaf__csf]

Would probably help if you'd tell the make and model of the car (and age.)

Whistling is usually related to belt slippage (the belt that turns waterpump, a/c etc.) If it's worn out you can change it yourself by loosening the alternator bolt which will make the belt loose. This is the same trick that will stop slippage if you tighten it instead of loosing and jerk the alternator to a 'tighter' position at the same time.

If the belt is worn out tightening it might temporarily stop the noise but then damage the water pump axle or just cut the belt in pieces while youre driving. Losing the belt means losing engine coolant circulation = very bad thing and you should stop driving immediately.

[AKS\/\/ulfe]

Thanks for the suggestions guys, I'll put it up on stands tomorrow afternoon and check around.

The description is pretty bad, mostly because I really don't know how else to describe it. Although, it does go away after a while. I'd say maybe after a mile or two, it stops making the noise and I don't notice it later as the day heats up.

By whistling hiss, I mean it sounds like gas escaping but in intervals where it gets louder then softer. Very quick, kind of in sync with the turning of the engine.

Seems to be primarily happening in the morning when I first get the car started.

It's a 97 Civic(non-riced), not really sure that'll help identify the noise.

Thanks again!
-SW

[eagl]

Good point about the vaccum leak possibility.  That will often be audible only at idle.

[Steve]

What Lazs said. Take a look under the hood before you put it on stands.. it may just jump out at you and save you some time.

I'd be inclined to consider a slipping belt if you described it more as a screeching sound than whistling hiss.

[SFRT - Frenchy]

Don't vaccum leaks also generate engine shake at idle, but goes away when you accelerate. My F250 had a vaccum hose disconected, and it was the symtoms. Gee, I spent a whole day trying to tune my Holley, befiore i noticed it:lol

[AKS\/\/ulfe]

Closer to a venting gas hiss than a screech, but I'll check under the hood before I put it up.

Thanks!
-SW

[Steve]

Good luck wulfe. I'm crossin my fingers for ya that it's something simple.

[AKS\/\/ulfe]

I'm hoping so too. After witnessing/helping/making stop gap suggestions to a friend that had to replace the boots on his car so he could sell it - I just want one of those easy tighten something fixes.

I never realised how hard it could be to replace boots, those rings that they ship with to fasten the boot to the axle require a special tool that we couldn't find to get them to tighten. What would have taken someone who knew what they were doing a day, took him/us a week.
-SW

[Siaf__csf]

The belt slippage is usually easy to spot, it hisses and screams loudly when you rev the engine. After you raise the revs for a longer period the belt sticks in and stops slipping so the noise goes away.

Check the belt tension by pressing the belt (from a free spot) with your thumb quite hard (with the engine turned off DOH). It should give in half an inch at maximum if not less. If it moves closer to an inch it will slip and cause all kinds of hissing and squealing noises.

Another source of noise could be your timing belt or chain not sure which one civic uses, probably the belt. The belt needs to be replaced every 70k miles or so depending of car. If the belt breaks or slips you can end up with busted pistons, broken valves, twisted crankshafts and all kinds of nice things. Basically it will total your engine. Some engines use small suspension/shock absorbers in the belt/chain which can also start to make rattling etc. noises inside the engine.

If its more like gas leak it could be anything starting from vacuum tubes to your exhaust manifold. Open the hood and rev teh engine by hand to spot the exact location of the noise. Just make sure you keep your hand away from the cooling fans and the turning belt. The thermostat controlled cooling fan can start even when the engine is off so never stick your fingers there with the battery connected.

[Hangtime]

Cat.

Check fer fur in the belts.

[SOB]

Somebody put Anthrax in your engine.  Quick, douse your car in gasoline and light it on fire!