Slight noise under hood/60-65MPH.. Help!

[roperteacher]

Hello! I am new to the board. I have been a CTD owner for 16 years and recently purchased a new 4. 5 4x2 600. I have read your info and decided to join this helpful discussion board!



MY Question... ... ... ... ...



When I accelerate to 60-65 mph ( approx 1600-1800 RPM) I hear a slight " Humming" or " Whining" noise from under the hood. When I back off the throttle pedal just slightly, it completely goes away! I can accelerate through it to 70MPH with no prpblems either! The only time I hear it is when I maintain speeds of 60-65MPH. If I set the cruise, goes away as well. Like I said, If I back off the pedal just barely, it goes away!! AM I just being paranoid?? DO I just need to get used to the " SOunds and girgles" of the new 04. 5 and get my 2001 out of my head???? Thanks in advance, and thanks for all the usefull info here on the board!! PS, everything is stock on this truck!

 

[jwilliams3]

I wouldnt worry about it.

I would just let it break in, and if it breaks it will be covered by warranty.



Could be valve train noise, but who knows.



--Justin

 

[GFritsch]

Turbo?

 

[roperteacher]

It's not the turbo... I love the whine of the turbo, it's just kind of a hummmmm... Best way to describe it. LOL It's not a vibration either, and really it's no big deal, just thought you knowledgable folks on here might have an explanation and put my mind at ease. . I am taking to a dealer this afternoon to drive with a tech and see what they say. Probably right, just needs breaking in...

 

[roperteacher]

Just got back from the dealer..... they said just like Jwilliams above to let it break itself in. Didn't think it was going to be a problem. . but seems to be doing it a little louder today. . still looking for any help anyone can offer!

 

[Blakers]

I believe they have a small, electric-driven, vacuum pump for AC controls. I think it runs intermitently as needed.

 

[roperteacher]

Thanks for the replys, could someone explain how the vacuum pump might corolate with the throttle/noise I am hearing. Any other ideas on what this thing might be? Drives me crazy to hear it! LOLOL roper

 

[amsoilman]

I believe they have a small, electric-driven, vacuum pump for AC controls. I think it runs intermitently as needed.

Unless the the 04. 5' models have changed from the 03' models, there is no vacuum pump. All the HVAC control valves/doors are run by electric motors. I had to Install a vacuum pump when I put the Exhaust brake on my 03'.



Wayne

amsoilman

 

[SRadke]

03's have a vacuum pump too. Like said above it's electric and very small. Mouted in the back of the dash I believe. Just to run the hearter control doors but not near enough for an exhaust brake.



I wonder if the noise could be an AC compressor? I can hear mine when it's on. It will run intermittently while the AC is on or anytime the defroster is on. If not it's prolly just that mighty Cummins trying to get you to turn her loose!



-Scott

 

[roperteacher]

I don't think it's an AC compressor???? You guys know more about this than I do! But, it ONLY does this while driving 60-70 MPH... and I can CONTROL the noise by letting off the throttle or pushing it back down... . You can play it like a fiddle... In fact, I played " Jingle Bells" with it today while driving down the freeway with the tech dude from the dealership... LOLOL Just drive it to 65MPH and you hear the " Howling noise" then let your foot off slightly and it goes away... you can tap your accelerator and sing any tune you want! Funny/... . but true..... I just hope it goes away! Any other ideas????

 

[amsoilman]

03's have a vacuum pump too. Like said above it's electric and very small. Mouted in the back of the dash I believe. Just to run the hearter control doors but not near enough for an exhaust brake.

My Repair manuel states:

Both mode control switches use electric actuators to control the mode doors. On all vehicles, the outside air intake can be shut off by selecting the Recirculation Mode with the mode control knob. This will operate a electric actuated recirculation door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.



Wayne

amsoilman

 

[roperteacher]

Will these actuators and air intake have an effect or produce a noise at certain speeds???? I'm trying to see how these replys may help me to go fiddle with the truck and see if I can't fix the problem myself... THanks for all the replys, keep em coming!

 

[MCornwell]

Vac Pump

Originally posted by Blakers

I believe they have a small, electric-driven, vacuum pump for AC controls. I think it runs intermitently as needed.

I hear the Vac pump every 1st start of the day after that never



hear it.



-Mitch

 

[FDrake]

Could the hum be from the fan. Maybe it isn't completely disengaging from the drive and is spinning just right at that speed?

 

[SRadke]

Wayne, a couple months ago I would have agreed with you. Then I became involved with this thread and was told I was incorrect. Now I don't know what to believe.



-Scott

 

[DPKetchum]

Wondering if your talking about the DRONE/VIBRATION thats been around since the 03s came out. The hydro boost hose noise???

 

[RobbieH]

Sounds like rear-end whine to me, even though you are saying it is coming from the hood. Your 4. 5 should not have the steering wheel drone like the '03 did.

 

[DPKetchum]

Do ALL the 04. 5s have the UPDATED hydro boost hose with the weighted dampner???Seems lots of 04s didn't have it.

 

[nickleinonen]

Originally posted by MCornwell

I hear the Vac pump every 1st start of the day after that never hear it.



-Mitch

i hear my lift pump every morning before i start it, but no vacuum pump

 

[amsoilman]

SCott,

ALl I can go by is what my Repair manuel says, and the fact that I have never been able to find any vacuum hoses of any sort on my 03'.



Wayne

amsoilman