Mechanics

CHEVY TAHOE

1998 Chevrolet Truck

I own a 1998 chevy tahoe. It has just hit 131,000 miles. 5.7 litre v8. On cold mornings, after my suv has sat all night cold, when I first start it up in the mornig it will make a whirring noise. That is the best way I can describe it. It only lasts a few seconds. Does anyone know what this could be and what should I do to fix it. Please help. Thanks : mrgreen: to me it sounds like some sort of pump or assist making this noise. As far as I can tell when sitting in the drivers seat, the sound seems to be located near the pressure assist for the brakes or somwhere around the computer system. It seems the longer it sit cold the longer the sound will last. Or maybe the colder it gets the longer the sound. Sometimes its maybe a split second, sometimes it seems to be 2 or 3 seconds, if not longer : : shock:
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Kelleneckert
January 22, 2007.



Noises are difficult to diagnose.
According to your input, You may have to check for piston slap.
Piston slap noise is generally a hollow noise, bell- like noise/ sound, when the engine is cold.
Usually the the noise will disappear after the engine warms up du to the aluminum piston expanding faster than the cast iron.
To eliminate this idea, you have to help me: before you start the car in the morning, remove the spark plugs and squirt a heavy oil on the top of the piston. Rotate the engine to allow the oil to seep pass the rings. Start the engine. If the noise is gone, the problem is probably piston slap.
Let me know, I will follow you up through this. : )

Tiny
Mathiaso
Jan 22, 2007.
Next time pop the hood before you start it. There should be an electric AIR pump, that could very likely be your noise. Could also be the Alternator, batteries dont really like the cold and it might be needing a little extra out of the alt.

Tiny
Jack42
Jan 23, 2007.
What does this small air pump look like and where would I be located. This sounds likely to be my problem

Tiny
Kelleneckert
Jan 23, 2007.
Ive seen them at the firewall on p/s and down low on d/s. Follow the AIR injection hoses hackwards from the engine

Tiny
Jack42
Jan 23, 2007.
Im having trouble locating the lines and the pump. Mainly because im not sure what im looking for. Lots or stuff on the fire wall. Anyway the sound is more like a short whine and not a whirring as I first described. Is this consistent with the air pump. I just started the vehicle up and it was a very short whine located it seems somewhere on the d/s of the fire wall. Do you possibly have any pics or anything that would aide me in my search?

Tiny
Kelleneckert
Jan 23, 2007.
Is it the area of the brake booster, maybe it has a very small leak. Disconnect and cap the vacuum line to the booster and start the truck to see if the noise is still there

Tiny
Jack42
Jan 23, 2007.
Thanks for all of your help. I believe I have narrowed it down to the alternator or the idler pulley. Again thanks for all the help

Tiny
Kelleneckert
Jan 23, 2007.