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What is this high pitched whistling noise??

87BrnRsd

87BrnRsd

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What is this high pitched whistling noise..EDIT PROBLEM IDENTIFIED!!

I started my truck up today and noticed that it was making a high pitched whistling noise from under the hood somewhere. I was driving it, and parked it for maybe 30 minutes, and when I got back in and started it back up is when the noise started. It sounds like it is comming from the passenger side engine compartment. I tried unhooking all of the vacuum lines that I could find but none had any affect on the noise. The noise only appears when the truck is stopped at idle in a any gear. When I step on the gas, it goes away. It also seems to fade a little if I drive the truck for about 10 minutes or so, but comes back loud as ever if I let it sit for about 5 minutes. It is very annyoing and I have no idea what it may be. Please help me!

BTW- It is an 87 K5 350 TBI
Thanks
-Harrison
 
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My car all of a sudden started doing that today also. Weird. Something to do with a cold fan belt is what I thought.
 
Could be a vacum leak or a bearing going south . Try taking off each drive belt one at a time . it's a good way to isolate the problem if it is a drivin accessory.

Just a thought , Tom
 
Ok I have some more info on the problem. I can rule out the waterpump because it is only about 1 month old, and hasnt even started leaking yet. As far as the drive belts go, I figure they would do it when its cold and not when its hot. I went outside a few mintes ago and started the truck up when it was completley cold, and it didnt make the noise. It only starts after the truck gets to operating temperature. It also doesnt sound like any noise that any belt could make. It may be a bearing but it doesnt really sound like that either. It is very very loud. Loud enough that my brother heard the noise from inside our brick house. I tried unplugging the vacuum hose that goes to the map sensor which seemed to quiet it down a lot, but still didnt get rid of the noise. Im stumped.:what:
-Harrison
 
87BrnRsd said:
Ok I have some more info on the problem. I can rule out the waterpump because it is only about 1 month old, and hasnt even started leaking yet. As far as the drive belts go, I figure they would do it when its cold and not when its hot. I went outside a few mintes ago and started the truck up when it was completley cold, and it didnt make the noise. It only starts after the truck gets to operating temperature. It also doesnt sound like any noise that any belt could make. It may be a bearing but it doesnt really sound like that either. It is very very loud. Loud enough that my brother heard the noise from inside our brick house. I tried unplugging the vacuum hose that goes to the map sensor which seemed to quiet it down a lot, but still didnt get rid of the noise. Im stumped.:what:
-Harrison
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Did you check that all hoses are connected?
There are some vacuum switches on the intake manifold that only open when the engine warms up. If there is a leak in the hoses on those it will only do it when warm and usually high vacuum is at idle.
That's my best diagnosis blindly.
Let us know what you find out.
 
Had a similar problem with my fan clutch when I smoked the bearings in it and almost shot it through the radiator. But who knows, there are different sounds for just about everything.
 
imiceman44 said:
Did you check that all hoses are connected?
There are some vacuum switches on the intake manifold that only open when the engine warms up. If there is a leak in the hoses on those it will only do it when warm and usually high vacuum is at idle.
That's my best diagnosis blindly.
Let us know what you find out.
Click to expand...
This sounds probable. I am not going to be able to work on it today because I am going to be busy at work all day. I am however going to have a free day tomorrow and Friday to diagnose the problem. It sounds to me like a vacuum leak. I was not able to check all of the vacuum lines last nigth, so I will start with those tomorrow. I will let you guys know if/when I solve the problem. Thanks.
-Harrison
 
I would check the fan clutch as said in previous post. Mine made a whistleing noise when it went out also. Grab the fan and try to wiggle it front to back. If there is any slop, the clutch is bad. A bad fan clutch will usually take the waterpump with it. I ended up replacing the WP, fan clutch, idler and tension pullys. Everything is nice and quiet now.

Also might check the Throttle body base gasket. I have heard them whistle when they get cracks and start to deteriorate.
 
Thunder said:
I would check the fan clutch as said in previous post. Mine made a whistleing noise when it went out also. Grab the fan and try to wiggle it front to back. If there is any slop, the clutch is bad. A bad fan clutch will usually take the waterpump with it. I ended up replacing the WP, fan clutch, idler and tension pullys. Everything is nice and quiet now.

Also might check the Throttle body base gasket. I have heard them whistle when they get cracks and start to deteriorate.
Click to expand...

My friend was driving my truck for a while and whne he returned it there was a few cuts in the hood fromthe inside out, turns out the fan took the water pump out and flew into the hood.
:(
 
MOABDADC22 said:
Sounds like a bad TBI baseplate gasket. Those things make the loudest shrill when they leak.
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That sounds very likely to me. My dad worked on my truck while I was at work today to try to figure out where the noise is comming from. He said it is comming from the back of the engine compartment, and he also said it may very well be the tbi baseplate gasket. I am going to a dear roast tomorrow at my local chevy dealership (I am good friends with a lot of the guys there), and I know that one of the guys will be able to diagnose it almost immediately. His name is Bill, and he knows more about chevys and how to diagnose and fix problems with them better than anyone I have ever met. Hes so knowledgeable, he can just about tell you every size of every bolt on the whole truck.:eek1: If he cant diagnose the problem, well lets just say I have never had a problem that he couldnt diagnose and give me exact instructions on how to fix it from the top of his head. Anyways, I will update tomorrow. My bet is the tbi gasket. Thanks for all of your help guys.:bow:
-Harrison
 
I went to the chevy dealership for the dear roast today, and my friend Bill found the problem in about 30 seconds. He used a can of air intake cleaner to spray around the vacuum lines and tbi until he hit the spot that made the whistling stop. Sure enough, the tbi gasket is leaking on the drivers side front corner. Im going to head up to autozone today and get the gasket and put it on maybe christmas day if I have time. If not, it will be monday. Thanks for all of your help guys.
-Harrison
 
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