Whistiling at 75 mph under mid-throttle - 04 Disco

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cornercase

Member
Dec 10, 2012
21
0
Los Angeles
My 2004 Disco has a bizarre and frustrating whistle that only occurs between 75-80 mph under partial throttle. It has done this for a long time and the only thing I can think of is that it is related to a pressure condition formed between the air feed for the climate control system and some check valve coming off the intake. It sounds like it's coming from the dash but honestly it's a bit hard to say for sure. It onsets at 75, disappears at 80, and also disappears if I just take my foot off the gas. If anybody has ideas before I start tearing into my various vacuum lines, it would be much appreciated.

Since I bought it, this noise has persisted through:
Rebuilt block (Cannibal V8) with new seprentine belt
New power steering pump
Completely new cooling system
Rebuilt serviceable front prop shaft
Disconnected radio (so it isn't alternator whine)

Truck is an '04 Disco HSE7 with rear A/C. Air suspension replaced with coils (compressor still installed), no ACE, OME MD front suspension/HD rear, stock tire size.

Thanks for your thoughs.
 
J

JohnB

Well-known member
Oct 18, 2007
2,295
12
Oregon
Since I have very rarely had my D2 up to 80mph tough to add thought to that although I had a whistle that sounds like what you are describing that was coming from the passenger side ac vent when it was closed.
Other things to check which I am sure you have would be window seals, door gaps, loose window frames, even the sunroof assembly where it glues to the roof could whistle if not seated correctly.


I know how these things can almost be a reason to scrap a car. I have a rattle in my BMW that is in the dash somewhere that has became such a focus to me while driving I'm about to scrap it.
 
helievacpilot

helievacpilot

Well-known member
Mar 29, 2007
960
0
Denver CO
x2 on the little shit. When I installed lights on my roof rack, I ran the wiring up the inside of the a-pillar out and around the rain gutter and right into a hole in the rack itself. Only about 2in. of wire showing, but all neatly encased in shrink-wrap. Looks factory.
One day, I'm driving along and I hear this really annoying whistle at certain speeds. Drives me nuts for weeks, until one day I happen to put my hand up to that area and discover that single bundle of wires, tightly tucked in close to the body, is my culprit!
 
C

cornercase

Member
Dec 10, 2012
21
0
Los Angeles
Hmm, I know one of the clips on the MAF-airbox tube is broken. Will duct tape that when I get home to see if it fixes the problem. Thanks for your thoughts!
 
Blue

Blue

Well-known member
Mar 26, 2004
10,080
885
AZ
Also consider your blower motor for the heater (located in the passenger footwell). Mine chirps at certain speeds/engine revs. Does your whistle only occur when the heat is turned on?

About the airboxes....those damn clips are shit. Both mine are broken again after I put in a new airbox. What a shitty design.
 
SGaynor

SGaynor

Well-known member
Dec 6, 2006
7,148
162
52
Bristol, TN
Check the black A-pillar covers on the outside - look for missing plastic rivets, or if it is loose. That will cause whistling (although generally at less than 75mph)
 
C

cornercase

Member
Dec 10, 2012
21
0
Los Angeles
Blue said:
Also consider your blower motor for the heater (located in the passenger footwell). Mine chirps at certain speeds/engine revs. Does your whistle only occur when the heat is turned on?

About the airboxes....those damn clips are shit. Both mine are broken again after I put in a new airbox. What a shitty design.
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Will check that as well. And as for those clips, I'm just going to fab up some sort of clamp that doesn't require the clips. I can foresee continuing to break them over and over.

I unfortunately didn't have a chance to try any of this and I'm headed out of town for a week but I'll report back once I finally get this thing in the garage and run some tests.
 
C

cornercase

Member
Dec 10, 2012
21
0
Los Angeles
Hey all, I just wanted to loop back since I got under the hood this weekend. I made a little zip-tie harness to pull the airbox hose onto the MAF. I couldn't get it to seat perfectly, but it was much tighter than before. I put 150 miles on it this weekend and the whistle is almost completely gone. Its so quiet, I might actually just be imagining it at this point. Anyway, I'm going to fab up a more permanent bracket but wanted to let everyone know that the airbox hose is definitely capable of whistling and whining at freeway speeds and certain throttle-load combos.

Thanks!
 
C

cornercase

Member
Dec 10, 2012
21
0
Los Angeles
number9 said:
Do believe there's/supposed to be a big o-ring in there.
......
Click to expand...
You're correct on that. Mine had it but because of the way it cracked, I'll fundamentally need a new airbox lid or I'll have to JB weld part of the crack. Since the clips on the airbox itself are broken too, I haven't decided if I'll replace the whole thing or fab a fixture for the lid and for the pipe. Seems silly to replace the whole thing if it'll just break again.
 
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number9

Well-known member
Nov 21, 2015
196
0
Coastal Georgia
Thanks and understand, one of the clip to areas of my box filter portion is cracked and did a work-a -round. OK at MAF side and if mine starts whining or whistling that will be first area checked.
......
 
H

Hubacek

Well-known member
Apr 28, 2015
88
0
Dallas, TX
cornercase said:
Hey all, I just wanted to loop back since I got under the hood this weekend. I made a little zip-tie harness to pull the airbox hose onto the MAF. I couldn't get it to seat perfectly, but it was much tighter than before. I put 150 miles on it this weekend and the whistle is almost completely gone. Its so quiet, I might actually just be imagining it at this point. Anyway, I'm going to fab up a more permanent bracket but wanted to let everyone know that the airbox hose is definitely capable of whistling and whining at freeway speeds and certain throttle-load combos.

Thanks!
Click to expand...

Search air box lid clip fix on LandRoverForums.com. Nice little mod that I used. I bought the clips at Lowes
 
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