"Thump" on Stat-up
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Joined: Dec 2006
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"Thump" on Stat-up
I have a 2004 Epeidition w/ 5.4l. Recently it stated mamking a "thump" noise immediately upon start-up. It will sometimes make the sound 1-4 times very fast, then quit. The dealer said it was the muffler. I say it is coming from the pass. side of engine. Any help appreciated.
chipperl
chipperl
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Joined: Apr 2006
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Oil in the A/C lines tends to accumulate at the low point of the A/C system - which, unfortunately, is the compressor. Upon start-up, if the A/C system is on, the compressor gets quite loud "slugging" this liquid through.
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Joined: Feb 2006
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My F-250 work truck makes a rather loud thumping noise upon startup as well. I have narrowed it down to the recirc door slamming shut. They must be vacuum operated. I haven't investigated further because it doesn't effect anything yet but I noticed toward the end of summer the A/C wasn't getting as cool so it might be hanging up part way closed. Fords are notorius for that. Had to fix quite a few of them when I worked in an A/C shop in Phoenix.
Check and see if you have a vacuum canister that has become disconnected, or a vacuum valve that is not closing properly.
Check and see if you have a vacuum canister that has become disconnected, or a vacuum valve that is not closing properly.
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Joined: Dec 2006
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No, It's not the A/C. My '99 F150 does that - it's not the same. It isn't the blend door either - already checked that. Of course I got it to the dealer and it will not repeat now. They said it was the muffler, but I can't see that. The noise is coming from the passenger side of the engine compartment under the hood.
Logistics Pro
Joined: Jul 2003
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From: Lawton, Oklahoma
Slugging like someone else mentioned is VERY common on initial startup and a very common complaint. Dont know how it would do it 4 times rapidly though so you may have some very odd Gremlin living under the hood.
cjsdad, on your F250 if it is a late model check the vacuum line on the water control valve under the hood. Its pretty common on these for the hose to get knocked off by oil changers during services. If you find it off just put it back on and after the vacuum builds up you shouldnt hear the noise on startup anymore.
cjsdad, on your F250 if it is a late model check the vacuum line on the water control valve under the hood. Its pretty common on these for the hose to get knocked off by oil changers during services. If you find it off just put it back on and after the vacuum builds up you shouldnt hear the noise on startup anymore.
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Joined: Apr 2006
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my 04 does the same thing. theres no word to describe the noise. my one question to you is how is your idle. my idle at around 10000 miles (now 21000) turned rough and no one could fiqure it out. I think the "noise" we are hearing is a misfire at idle. I say that because somtimes when it does it it sets off my smoke detector in my garage( at last check these trucks dont smoke)hopefully this will help someone find a cure!
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