constant Whistling noise after engine warms up

[rs4rep]

So I have a 2004 A4 1.8t quattro 6spd, with 148K on it. In the past few weeks I have noticed a whistling noise coming from the engine bay. it is a constant whistle, giving it gas has no effect on it. If i turn the car off and let it cool down a few minutes it doesn't whistle right away but will once it warms back up. I have no CEL's and it is driving me nuts trying to find the issue. Does anyone have any ideas on what it
could be, any help would be greatly appreciated.

[Kwarner]

Have you checked all your valves? Could have a cracked/split one out of the thousands on the 1.8t pcv system.

[Charles.waite]

You probably need to get your whistle tips adjusted. <insert Bubb rubb video here>

It goes woo WOOOOO!

/useless post

[jc_333]

I have a similar whistling sound but more like a rattle snake tail when engine is cold. The rattle sound increases with revs and sounds different in and out of gear. However, once engine warms up the noise is gone so starting to think it could be a loose exhaust gasket or something?

Any ideas?

Thanks

J

[bull1780]

Could be your secondary air pump. It will typically turn on at cold startup and when it goes bad it will begin to make a loud whistiling noise. Most of the time it will not throw a cell. That pump is designed to warm up you catalytic converter at cold starts to reduce emissions. Has no effect on driving at all and most people dont replace it since its a pretty expensive pump or unless you need to pass emissions in your state.

[rs4rep]

Could be your secondary air pump. It will typically turn on at cold startup and when it goes bad it will begin to make a loud whistiling noise. Most of the time it will not throw a cell. That pump is designed to warm up you catalytic converter at cold starts to reduce emissions. Has no effect on driving at all and most people dont replace it since its a pretty expensive pump or unless you need to pass emissions in your state.

Here in Hawaii I don't think I have to have emissions to pass, but do in VA and thats where I am going back to soon. I am going to be getting rid of all the SAI pump and all the emission stuff soon once I start my build. Just gotta put up with it a little bit longer.

Also like I said it only does it once the engine has warmed up, cold I have no noises at all, then about 30-45 minutes into driving I will start to hear the whistling.........it sounds like its coming from around the front left corner near the turbo but it doesn't sound like its coming from the turbo.....changed the line on my Diverter valve today and checked all around there so will see if that fixes the problem tomorrow......

[rs4rep]

This may be a leak or hole in the hose of the vacuum. When you increase the speed by pressing the accelerator pedal, the pressure rises in the pipes make a hissing sound. High pressure drops when you release, and the sound disappears. Have someone hold idling so you can locate the leak. In addition, many high intake air flow and some stock air intake make a whistling noise at high speed. This can be controlled with a little reving the engine while someone is listening to the air intake.

And also check the vent pipe of the PCV valve and PCV valve itself. It 'is blocked? you can look for some Audi repair for some guide about what to do with the whistle sounds..

The only problem with this is that whether I am giving it gas or idle the whistle is constant......meaning that no matter what is done the whistle is the same frequency and doesn't change with or without gas. So it makes it hard to locate it by having someone hold the gas to try and locate it.......I am going to check all the PCV valves this weekend when I have time if the whistle wasn't fixed today by what I did..........Also I have had the K&N filter in the car for the past 2 yrs so there is no reason it should have just started whistling within the last month......