I searched, but only found whistles on acceleration. Running at 70+/- when I let off the gas or the cruise coasts, there is a whistle. It is vacuum, not drive train.

I visually inspected all of the vacuum lines I can see under the hood, and will start a replace them all project, but this sounds like it is under the dash or close to the driver's side fire wall. After time in the workshop manual, the cruise control is vacuum operated so this system would be the first area to start looking. Anyone else had this issue or have any direction that might save time?

Just put six hundred miles on the Disco and the coolant level held. Still need to replace some seat motors, u-joints, flush brake fluid and I am considering the thermostat conversion.

 

Smoke test - inject smoke into the system (Halloween party smoke machine), or cigar smoke. Some also use an UN-LIT propane torch, if the vac system sucks up the flamable gas, the rpm will change. Of course, if the right spark happens, could burn off your eyebrows. Can also attach a vacuum guage, and while that is monitored squeeze off flexible lines to look for change. Don't squeeze the hard plastic lines.

 

Any updates on this?

I'm having this same problem. I had one cracked hose right at the cruise control's vacuum control unit. I replaced it. Now the whistle is constant unless accelerating (idle, deceleration, cruise engaged). It sounds like it's coming from a hose at the top of the back of the engine (closest to the cabin), but it'll be tricky getting to those hoses to tests for cracks. So, it'd be great to know if my theory is correct before diving in.

 

The cruise control vac system runs from a separate pump, not part of engine vac.

Main engine vac hoses are shorty from fuel pressure regulator to intake (driver side rear), a line from each valve cover, one to throttle body, one to intake (passenger side). Those are the crankcase breather system, and the one on passenger side needs to be pulled out of the valve cover and cleaned with solvent. And big line to power brake booster.

You can also restrict air intake and it will make vacuum leak sing louder. You can also wave a propane plumbing torch (un lit) around gaskets to see if idle changes.

 

I have been told by a mechanic I need an Idle air Control device and the cost is 495 plus labor. My car whistles... Any suggestions? It is a 2002 Land Rover Discovery II.

 

I would want to be very sure that it was the part and not just a hose attached to it. A wet rag held around the hoses and clamp areas, and the IACV itself may make the noise change. A cracked hose under the crimp on clamp could be the issue. Or it could be elsewhere.

That part is $359 at Atlantic British ( Stepper Motor (IAC Valve) BOSCH Engine (Genuine Part # ERR6078) - Land Rover fuel injection from Atlantic British )and a little over $200 at Rock Auto (aftermarket AC392). Also available at salvage yards for maybe $20 (you pull, then you know how to put it back). Some one might post a known common substitute.

The attached page shows the unit, you would need two new worm drive hose clamps, the originals are crimp on style (one time use). Attached picture as well.

With two bolts, one plug, two hose clamps; maybe 30 minutes for a slower mechanic. Truck will "adapt" to the new unit after a period of driving.

IMHO, you might wish to seek another mechanic and share these pages with them. Or join the DIY side. Or suggest different souce of supply for your mechanic.

Now if the unit is leaking and making whistles, mabe just a new clamp or hose. If the unit is not working properly, maybe remove (two hose clamps), and squirt carb cleaner inside the business end of the unit to clean out any gunk. The units of D1s are different style, but do the same thing, and are cleanable, and a lot cheaper. It is a 180 - 200 position stepper motor that is used as a computer controlled vacuum leak. Gunk on the pintle area keeps it from closing all the way. May be worth cleaning if he has not done that.

This unit is also used on a lot of BMWs.

BMW530I(1994 - 1995)
BMW540I(1994 - 1998)
BMW740I(1994 - 1998)
BMW740IL(1994 - 1998)
BMW840CI(1994 - 1997)
BMWM3(2001 - 2006)
BMWM5(2000 - 2003)
BMWZ3(2001 - 2002)
BMWZ4(2006 - 2008)
BMWZ8(2000 - 2003)
LAND ROVERDISCOVERY(1999 - 2004

It is a Standard Motor Products AC392. Also available from Airtex/Wells.

Would I trust one from a salvage yard at $20 or so? Do partz vulturz have feathers? Yes, but I would clean it before install. Since there are so many bimwah's it fits, easier to find.

Seems to me your mechanic is using OEM parts, perhaps even buying from dealer (highest possible price). Can't blame him for using new oem, he has to live with a warranty. In most cases he would resist using pre-owned parts except in emergency. I don't think he has fallen into association with this guy - yet.

But at the end of the day - three Ben Franklins buy groceries (well they used to).

 

Are you people sure that the whistling sound is not the wind outside hitting the roof rails or any other part of the truck. It could also be the transmission, drive shaft, or transfer case that make that noise after a certain RPM. If the truck runs fine and you don't have any codes or dash lights on than I would be a little hesitant to start throwing new and costly parts into the truck.

 

re: I have been told by a mechanic I need an Idle air Control device and the cost is 495 plus labor

certainly there are several kinds of problems that can cause vac and similar noises. I was basing my response on the pro's diagnosis. One pro that frequently posts mentioned pushing a clean (new) oil filter into the air intake hose, which will make any vac leak scream a lot louder, easier to find.

 

Ok fellas, ive read through this thread and there is some great responces, unfortunately I have this issue as well. Hear is what ive done to date, Replaced all soft vac hoses, did the eather test, changed the IAC, New pcv hoses and sep. replaced any soft or older looking vac hose. Still no change.
Symptoms: whistle constant after warmup, seems like something closes after operating temp and insta whistle..and its LOUD. Pre warmup, whistle on release of accel. stops at 800 rpms, The whistle changes timber thru the rpm range, varies almost like a bad reed in a musical instrument. Thoroughly befuddled on this one folks, get your thinking caps on and help meh !!

 

Where OP is describing the sound is coming from, I would take a close look at the brake booster.