LOUD KNOCKING UNDER DASH? (passenger side)

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Feb 15, 2011 | 01:40 PM

05truckguy

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LOUD KNOCKING UNDER DASH? (passenger side)

Any expert advice here would be great-

Truck-2005 F-150 XLT 5.4L

Problem-Currently when my truck reaches a speed of 45mph+ there is a methodical knocking sound that comes from the passenger side dash. This sound is on the interior and comes from the far right corner of the dashboard.(almost as if someone is tapping with there finger every other second). There is no correlation with anything else being turned on or off that affects this sound.(i.e. air) It simply happens once I reach a certain speed and is not an outside noise. When I slow back down under 45 mph the knocking subsides. Has anyone ever experienced this? Any suggestions?

Feb 15, 2011 | 03:57 PM

MCDavis

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From: RVA

When you get above 45, does the knock continue at the same interval when you're doing a higher speed, say 65, 75? Just trying to get more info out of you.
Does the knock sound hollow? Like a dead blow hammer on wood, or a ping like metal on metal?

Feb 16, 2011 | 12:08 AM

Shooter00

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From: Okie

Probably a Tommy Knocker. Just leave him some milk and cookies when you go inside for the night and it should subside! LOL

Feb 16, 2011 | 08:44 AM

05truckguy

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The intervals do not change as the speed increases, and the knock is a hollow wood sounding knock. It sounds like someone is tapping the plastic underneath the dash in the far right corner of the passenger side. ( I wish it was Tommy Knocker and some milk and cookies would get the job done.)

Feb 16, 2011 | 02:47 PM

planehunter

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Joined: Aug 2010

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From: Vancouver, WA

Was your truck made in Mexico??? LOL Just kidding. I had a similar problem on a car I had, found out that the windshield trim was lifting slightly at highway speeds. My guess is you have something similar but perhaps in your fenderwell or under the hood.

Feb 20, 2011 | 06:50 PM

Millzy

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From: SW Ontario

Try and adjust the temperture controls from hot to cold and see if the noise changes. I think you have a problem with your blend door motor.

Feb 20, 2011 | 07:03 PM

screwy

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Joined: Aug 2002

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From: Over Yonder, MN

This is just a wild shot in the dark, but on the far right of the cab is the recirculating air door. I wonder if it has somehow broken loose of its motor and is flapping about, maybe at speed the air pressure produced is enough to cause it to bang? That’s the only thing over there I can think of that might be remotely affected by speed, unless it is truly outside the cab. But I'd also expect that I'd be heavily influenced by the blower speed...