Thump just after starting engine

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Feb 27, 2006 | 11:18 AM

Jwinterstein

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Thump just after starting engine

When I first start my 04 Larriat - after about 20 seconds or so there is a "thump" that sounds as if it is under the passenger side floor board or dash area. I thouht at first it was a heater "door" closing or opening but now am not sure. Any ideas?

Jim

Feb 27, 2006 | 12:54 PM

alpcrc

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From: North Carolina

Me Too

Jim-With you on the "thump". My '04 XLT Scab 4x4 does the same thing. Stealership can find nothing.

Feb 27, 2006 | 11:04 PM

xtrm1stang

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Joined: Sep 2005

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From: Florida

Try starting your truck with the a/c in the OFF position. See if the noise is still there, then turn the a/c on and see if it happens within 30 seconds. The a/c compressor will make a pretty loud thump/bang noise when it is first engauged after sitting. This is normal and is caused from the freon setteling in the ac compressor. if you drive with the ac off first, once the trcuk is warm it will most likely not happen, even if the ac has not been on yet.

Feb 28, 2006 | 08:25 AM

poolmanj

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Joined: May 2004

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Mine does the same thing.Don't think it has anything to do with the A/C comp.I think it is more like one of the blend doors resetting it position but I am still searching for the answer.

Feb 28, 2006 | 12:56 PM

Jwinterstein

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Thanks, guys - my impression too was that it was a blend door. I will try the suggestion, however.

Jim

Mar 2, 2006 | 09:31 PM

Bozack

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mine the same / no clue & have wanted to post about this BUT had no idea what to say - THANKS

Mar 2, 2006 | 11:44 PM

edgl

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Joined: Dec 2003

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From: Lancaster, CA

My last few Ford trucks did that. My 06 F350 does the same thing. It is the A/C system. It comes on after you start your truck, in about 15 seconds, if you have the A/C on.
Ed G