Howling Noise { Not Casper }

[Road Kill]

I have discovered an intermittent howling noise at free way speeds. Sounds like it is coming from under the hood. Kind of like blowing into a bottle and making it howl. :confused:

[imported_]

Engine cooling fan cutting in most likely

[Jimamatic]

Road Kill,
I've got it too. But it does'nt start until around
70 mph. Or, if accelerating hard getting on the
freeway. Seems to be more pronounced in cool moist
conditions. Called a service tech months ago about
it. His response, "If you stay under the speed
limit, you will not have a problem"... Unfreaking
believable. The real funny part is he was serious.
My guess is that it's the turbo. My father-in-law
has a FPSD and it does it too. Have not pursued
any further...

[mdrag]

Jimamatic,

Tell your service tech you were traveling through OK where the LEGAL speed limit on interstates is 75 MPH... :D

Road Kill,

I'd tend to agree with MaD MaX - probably the cooling fan kicking in, it is quite noticable when it turns on.

[dmaxstu]

I've found this truck makes all kinds of different noises at different times. I think if you start paying attention to them it'd drive you crazy.When you hear a noise one day it is gone the next.Just keep driving that sucker and keep an eye on the guages, check the oil regularly,and look underneath for possible leaks. I imagine for most of them after 200,000 miles you'll still be doing that routine and nothing will have happened. Stu

[Vincent]

It's your air conditioner doing it. Mine does it too, like you said, only above 70 mph.

I verified this by turning the air on and off above 70 mph...definitely made the noise come and go.

I talked to the service manager about it and he told me the only way to solve it is to lengthen the coolant/pressure hose and insulate it with really thick insulation wrap. They did this with an angry customers vehicle and it made it much quieter.

[Road Kill]

Thanks very much for all the input guys. The air conditioner is possible as I just started to use it lately. I was running about 75 with the air on when we heard it. Could be cooling fan also but it is the 1st time I noticed it and should have heard it before. I will check out the air conditioner theory and report back. Just for the record my dealership service is very poor. I hope I don't get anything bad wrong. Thanks again. :cool:

[Dinkie Diesel]

I think Vincent has hit the nail on the head. Mine does it too. I turned the A/C on and off during a trip to Ky. and it is definitely related to A/C. I was going to ask about it here on the forum but it's kind of hard to explain these little noises sometimes. I would have never guessed the hose/insulation as a resolution. I just thought it was a noisy compressor.

[IndigoDually]

Insulate what hose? Where? With what? Just want to know for future reference.

Thanks, John

[Road Kill]

Well guys in my case it is not the air conditioner. It made the noise both with air on and air off. I am leaning to cooling fan or turbo. Truck runs great and I am hard of hearing so the heck with it. Drive on! lol Thanks for all your input guys. :D

[Kennedy]

Hmmm, if I had read the thread when first posted...

We were just through Midland, and actually spent Saturday night in Auburn...

[RealBigTruck]

Nope, I don't think it's the cooling fan or the turbo. Those are both very distinctive. Cooling fan sounds like a B-17 taking off. Turbo is a whistle that increases to the point that only dogs can hear.

I have the same problem and it is NOT AC related. Happens over 70mph or a little lower if there is a headwind. This "blowing in a bottle" sound is something airflow related at the base of the windshield. I haven't been able to find out exactly where yet.

It does drive me crazy though. Nice quiet ride interrupted by intermittent howling that I can hear over the radio.

[Road Kill]

Dang, I would have been very happy to meet you John and better yet I have a spair bed room. lol Real Big Truck we are hearing the same thing and I am stumped. Wife says it is out side wind noise . She is not often wrong! lol Just to share info. I had the wind shield noise and used some Dow Corning RTV Aquarium sealer to go down both sides, (vertical) with a small bead of RTV. End or noise! Big thanks to this forum, great as always! Now about Casper? :cool:

[Lawnboy]

Just throwing an idea here.... You say it did it with the A/C on AND off. How do you know it was really "OFF"? From what I hear, the A/C compressor is activated in all but one dial position! Maybe just for a test, try unhooking the clutch wire connection.?

In some of the older C/K trucks they had a TSB about A/C compressor groaning and it involved a replacement compressor mount that would somehow not transfer the "normal" howl/groaning through the engine/driveline.

[Vincent]

Lawnboy is correct. The a/c compressor will turn with even the vent/fan in the blowing position.

I've personally verified this...considering that I live in New Mexico (read: hotter than all get out) I run my A/C quite often.

It will indeed make the humming noise above 70 mph. listen to it as it cycles on and off, then you'll become believers. ;)

[Road Kill]

Learning every time I get on the forum. I will try to make sure the air is completly shut down for next test. We had the air on at 75mph on the freeway, and it was howling. Just hit air off and it still made noise. I did not think to change the control setting. Thanks guys, I will report back. :rolleyes:

[neophyte]

OK. Here's a new one for you...I just heard the noise, along with everyone else in my truck at the time...a howling sound with the a/c on but not at high speed. I was coming to a stop sign when I first heard it! Like a mad person obsessed with any new noise, I have been driving around with the windows open and no radio, with the a/c on and the a/c off listening for that sound. It happens with the a/c on only but at low speeds.

[moisheh]

My a/c has done this since new. starts to "whine" at about 68 mph. Shop foreman looked at it last year and said nothing sould be done. The mounts for the compressor are pretty beefy. I had it in this week and they replaced the belt tensioner. Noise is still ther, but not as severe. If you have this noise get your shop to notify GM. If enough people complain there will be a fix.

[mdrag]

Topic moved to 2500HD/3500 HD Trucks & Drivetrain Forum.

[Road Kill]

After a trip to Indy and back to mi. I am convinced the howling noise is in fact my air conditioner. I will get dealer to record it . Thanks to you all.

[Tommy turbo]

Took my truck in today for the updates and airbox replacement and told the service writer about the same noise in mine. It is definately when the compresser cycles on and off, and I would describe it as a slight rearend howl but coming from undere hood. We will see what they do.There were ten items on my list. I will tell you if they find anything.

[Reno DMAX]

Wanted to bring this back up;

Has anyone received a fix for this condition? I am experiencing it also and wanted to know a little more before taking my truck into the dealer.

[moisheh]

I have had this problem since the truck was new. Had it in twice. They replaced the belt tensioner, but it did not help. Gm is aware of this, but there is no fix. It drives me crazy!

[c5dura]

I have the exact same noise (like blowing into a bottle type howling). It only happens when I really get on it accelerating and not until 2nd gear. It will also be there constantly when going uphill, pulling a heavy load, or going faster than 75 mph. In other words, you have to really push the engine to make the noise appear.

It is NOT the AC, I've been having this sound all winter and spring and have had the whole computer climate control turned off.

It is NOT the cooling fan (I'm very familiar with that sound as it is quite a bit louder and only occurs when its 80 degress or more).

It is NOT the whistling Turbo sound.

It is NOT the radio (I have an aftermarket unit).

I just added a 2nd alternator, so I don't think its the serp belt (I had to get a larger belt and add a third pulley). I would think the noise would have at least changed if that was it.

I suspect it might be something along the lines of a restriction in the intercooler and/or related plumbing or something like that as the howling only occurs during high boost operation.

Anyone got this one figured out yet?

[ 04-15-2003: Message edited by: c5dura ]</p>

[Burner]

I did not look...... Does it have something to do with 4x4? Is there a 2x4 that has this problem? If the switch is bad, would it make the noise if 4x4 mode applied? :confused:

Burner--------&gt; :D

[c5dura]

I don't think this sound is related to 4x4 as I run in 2x4 on the highway when experiencing this. Besides, the sound comes and goes with the amount of boost, not ground speed.

C5dura

[dmaxalliTech]

Road kill, where are you getting you truck serviced? I used to live in the tri-city area and graduated from Western High in Auburn. I have worked at Labadie, Graff and Draper in the area. No money over there, moved to Grand Rapids...

[LittleBigRig]

Mine is definately the cooling fan!

I was pulling a long serious grade with my 34 foot travel trailer in tow. Duramax and Allison were getting a good stretch - at 70 mph, the tranny was running the engine just barely below redline. I let it run there for a couple of minutes just to see how things performed - while keeping a careful eye on the gauges of course.

Then, the strange howling that I had never heard before winds up gently from under the hood and continued to run until I topped the hill. Then it slowly wound down.

The tranny and engine temp gauges moved upward, but no where near any danger areas. In my case, the powertrain management system called for additional cooling and it got it.

[01max]

we had 2 01 making the same noise when the ac comp kick on. after some time talking to gm we put a comp. from a 03 truck on it and had to get a special suction hose to make it fit. the noise was gone for good.if anybody is interested i could try and get the part #

[madmatt]

if this is the noise I think you all are talking about, it is liquid refridgerant getting into your a/c compressor, the fix is to R/R the compressor, put the updated low side line on and usually the a/c belt tensioner is broke as well so it'll probably need replaced to. as I've said before ....there is a bulletin on this as well.

[Inspector]

Just for grins and giggles try this. Run some masking tape over the left and right side mouldings of the windshield. If you have a bug deflector on the hood the air flow is disrupted just enough to cause a wind noise along those mouldings. Do that and take a drive to 75mph or whatever and see if the noise goes away. The fix is to reatach those mouldings.
Denny