Intermittent Humm / Rattle in Dash

[bigflatdaddy]

My truck is driving me crazy. At about 80,000 miles, it developed this hum/rattle somewhere in the dash, somewhere between the stereo and the passenger side. It is really wierd - lasts for about 6 seconds, off for 5 seconds, back on for 6 seconds, off for 5 seconds, and so on. The only time I can't hear it is when I have the stereo blasted - and I can't do that all the time with the kids in the truck... ... ... ... ... ... ... .



I can't figure it out - can't feel any vibrations that match the sound...



Got any ideas?



Thanks - Paul

 

[rbattelle]

First make sure the glove box is empty.

If the sound is still there, remove the glove box altogether.

If that doesn't cure it, then it's time to start digging around behind the glove box.

Do your HVAC vent selections work properly? I mean, are you getting air out of the vents you select? If not, it could be the dreaded broken blend door and pieces of it are rattling around the HVAC system.

Ryan

 

[bigflatdaddy]

Glove box not a problem - sounds higher in the dash. Will check out the HVAC. Occurs independent of fan.



Any idea what is going on/off with that pattern?



Paul

 

[rbattelle]

Any idea what is going on/off with that pattern?

The only thing I can think of would be the A/C compressor. I know my truck vibrates a lot more at highway speeds when the compressor cycles on. The additional vibration could cause something already loose in the dash to vibrate. Try turning off the A/C (remember it comes on in defrost mode).

Gonna be tough to find it, though.

Ryan

 

[bigflatdaddy]

It doesn't seem to cycle with the AC. Happens even with everything off. I'm thinking of sound-cancelling headphones.....



I was hoping that cool weather would help - but no change... .

 

[CPittman]

Mine's doing the same thing... is it some kind of vacuum pump that's cycling on to maintain a vacuum on the braking system? Does the braking system have a vacuum boost / assist?

 

[hintonJ]

My '03 did a similar deal. So, I drove it around with a big heavy book on the dash and moved it around until it stopped. It was a gap in the dash and glass that was rubbing, stuffed a little weather stripping behind it and it went away. .

 

[Hincka]

I also had a wierd rattle/vibration in my dash a couple of months ago, the dealer thought it had to do with the busted blend door, but when they repaired it, the noise was still there. It ended up being the auto trans dipstick resting on the firewall and rattling against it. Bent it a half inch and problem solved.

 

[CPittman]

Do our trucks have a vacuum pump for brake assist? Mine sounds something like a large fish-tank air pump cycling on and off. You can turn the key to the 'on' position without starting the truck and you'll hear the sound. It is either coming from under the driver's side dash or in the engine compartment at / near the driver's side firewall. My truck has the lift-pump retro-fit so the lift pump is in the tank not under the hood. I'm wondering if it is caused by the CP3 somehow - 176K miles on the '04...

 

[TCDiesel]

Be careful when moving the trans Dip stick Tube, I have seen several rub against the High pressure AC line. . $200 repair plus Down Time. If this happen in the Winter months with no liquid it may destroy the AC Compressor.

 

[bigflatdaddy]

Thanks for the info - still in same situation. It'll be a cold winter with my head hanging out the window like an old dog.....



Paul

 

[Pawpaw]

This is gonna sound dumb, but check your jack.



A couple of years ago, someone tore their dash half apart trying to find a rattle and it turned out to be the jack.



Bob

 

[bigflatdaddy]

Well, it sounds like the same thing Pittman has - I was fumbling around and noticed that it happens when the engine is in on, but the engine hasn't been started..... Any ideas? I have a pair of wire cutters... ...