Strange Noise

[76okievette]

Well, last night was the third time I have heard this noise its hard to describe but here goes,
its a rpm related noise, only hear it when car is warm and moving, its not a metal on metal noise no metal sounds at all, its more like a low pressure release every two or three seconds, kind like pssst, pssst, pssst, but I can't hear it when the car is stopped even if I rev the engine, it sounds more like its coming from the front center of the car, I have looked and can't see any thing rubbing on any moving parts, so I am thinking more like a gasket releasing pressure ever few seconds. Anyone have any ideas of where I should start looking???

 

[bill81vette]

i'm thinking either a fan blade rubbing against its shroud,or a pulley rubbing against something,also check your water pump to be sure there is no play in that pulley

good luck...bill

 

[Fishman]

If you have an automatic, have someone get in the car, hold down the brake pedal hard, put the car in gear and give it a little gas.

If the fan blade 'walks' into the shroud, you probably have a busted motor mount.

 

[76okievette]

Great suggestions, I did not think of the fan blade at all, I will check it out tonight. I appreciate the ideas.

 

[sherry_ridgeway]

hi
Be sure to check around the headlights where the vaccum lines are attatched,
Unless im mistaken they"doors" do open and close from a vaccum ,
Sherry

 

[curtis]

If the noise is only when you are moving, you may have a nail in a tire and when the tire rolls over it, it cocks in the hole and pssst.

 

[76okievette]

Hey, thanks Sherry I will check the light doors it could be a vacume leak, your car looks great by the way.

 

[brusso]

Something wet dripping on the exhaust manifold or pipes? Do you have A/C?

 

[76okievette]

Well I checked all the suggestions, and yes the car has A/C but I have it shut off, and have not found anything. I drove the car into work this morning and the noise was still there, its getting louder, it kind of sounds like a leak in the exhaust manifold gasket that is blowing air out once the engine warms up, thing is as I slow down I hear the noise (almost a flapping type noise) its loudest when I back out of the gas and the car is moving but the engine is at a low RPM, but when I get stopped and rev the engine to try and locate it the noise is not there. I guess since it's getting louder it won't be long until I find out what is going on. Anyone else have any ideas I can check it would be appreciated.

 

[bill81vette]

check to see if you have a separated tire on the front axle!!!!



bill

 

[sherry_ridgeway]

do this to be sure
take a bucket of VERY soapy water and using a wash rag , spread it all over the lines under the hood "engine running" and warm ..."not on the plug wires" or distribuitor, but all the other ones check for bubbles and or leaks, it's most likely a leak in a vaccum or a leak in a line someplace,, next check for relay probs with a volt meter or an engine analyser, get a can of electrical contac cleaner and take apart the fittings "engine off" and spray them pretty good make sure all the connections are good and the wires are all routed properly, "no kinks/no burn spots/ ..the noise sounds like "to me" to be a vaccum leak someplace espesally since it only does it sometimes "after pressure is built up"..after doing this start the engine and check all the other electrical devices ie clock/headlights/instrument panel/ tail lights/radio/blinkers/etc..if it is somenthing electrical its pretty much a hit and miss proceedure,until you find the proper relay, my true feeling is that its a vacuum leak in a line someplace and easily fixable with a few feet of hose and a few replaced clamps, be sure to also look at the vaccuum hoses coming from your distribuitor going to your other componants that feed off of that
just an idea
Sherry

 

[curtis]

could be a leaking header gasket or a loose spark plug.