Does anybody know what would cause my truck to whistle when I turn it off. It also does it when I start it up most of the time. It sounds like its coming from the passenger side of the engine near the windshield. Sorry for the vauge description but I don't know anything about engines and I don't have haynes manual, my nearest autozone didnt have one for my year and havn't gone to another yet.

 

Is it your HVAC system leaking the residual vacuum out? The blend door and defrost/dash/floor selections are all vacuum controlled.

 

i would guess an air leak on the intake somewhere, its the only thing i can think of that is in that area and make a whistling sound without making other symptoms. if it were a vacuum leak you probably would have a trouble code or other symptoms. first go buy the repair manual, then check the air intake for cracks and leaks. i bet someone changed the air filter and didnt put the intake back together correctly

 

thanks for the replies.
Its possible that the air filter got changed about a month or so ago we had work done on the truck because the speedometer was not working correctly(it wouldnt move until roughly 70mph), actually I think it was probably the speed sensor or what ever, but in addition to that the mechanic had to replace somthing else, im not sure what its called but it did somthing with the idle speed and was causing the truck to stall when coming to stops (that was annoying specially since it made steering very difficult) anyways, I am not sure if the mechanic replaced the air filter or not, my dad might know, but when i talked to him he after we got the truck back he didnt seem to know much of what they did with the truck. I'll keep yall posted as I figure things out, its hard when i dont have time. Do you think it could cause serious damage if this doesnt get fixed real soon.

Like i said i dont know much about engines but is the intake supposed to build pressure at some point cuz, i think what ever is making the noise had to have some sort of pressure and so when I turn the key so the truck is off the pressure is released and vice versa when starting up or within a few minutes of starting up. Anyways thats just my thinking

 

not pressure, vacuum. the motor acts like a giant vacuum, air is sucked into the top of the motor and combusted then goes outt he exhaust. when you stop the motor the pistons rotate a few more times and continue to suck air, but only for a second. pop your hood and check the big plastic tube thing on the passenger side, there are some giant hose clamps holding it together. just give it a good visual inspection and check for leaks. when in doubt find someone that knows what they are doing, this is a very simple job

 

Whats the best way to check your leaks? I think my grandpa used to pour water on the tubes and checked for bubbles, is that way it is normally done? Is there somthing I should be careful of doing this. Also what is the silver thing circled in the picture, the metal tubes on top are cold and have condensation on them, it's probably normal but it sounds like that is the area the whistling is coming from when I turn the engine off. My guess is that that things has to do with the A/C since its cold, but ill let you guys tell me what it is. Imma go back out and look around somemore

EDIT: I found one of those big round clamps really loose the one that goes from the back of square plasitc thing towards the cab but that didnt change anything with the whistling when starting up and turning off, but it did make the engine sound a little better, it sounded like it had more power, maybe it was just me cuz I was excited it might have fixed the problem, but it didn't.

 

yea that tube that you fixed the clamp on is part of the intake. the silver thing in the picture is part of your air conditioner. dont spray water out of a hose, you can fill a spray bottle with just a drop of soap and the rest water. spray it in the area that you think is making the sound, you should be able to see most leaks. you can also double check the long rectangle box thats attached to the tube you adjusted, its also part of the intake and could whistle if it were loose

 

Yea I checked the clamp for that both on the inside of the box and out side, actually the rectangle box doesnt have top on mine like it did in the picture but they were all tight. If it were a leak in the intake wouldn't it whistle at all times not just after starting the truck and after shutting it off. While running I do not hear it

Thanks again for your help, I am sure we will get it figured out but not tonight cuz im too tired

 

yea it would whistle all the time but you might not notice it over the engine noise. try the soapy water trick

 

I don't think it is whistling all the time because when I turn it off, everything is quiet at first then a few seconds later the whistling starts for 15-20 seconds and it starts loud and then gets quieter as it goes. And when starting up I don't hear it initially but a few seconds later it starts and then goes away after a few seconds. Not sure if it would help but I could probably get an audio clip of the whistling.

EDIT: I think it is somthing with the Air Conditioner because I tried it with the Air Conditioner turned off and there was no whistle. If you want to hear the whistle, I have put them here.