another engine noise
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another engine noise
When starting the truck cold it makes a roaring noise for a couple of seconds I have been told that this could be the fan also after turning on the air it makes a very loud thump has anyone else experienced these problems?
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Joined: Apr 2002
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From: Cary USA
another engine noise
[updated:LAST EDITED ON 26-Apr-02 AT 03:48 PM (EST)]About every third or fourth startup (cold start), mine seems to do the same thing. Its almost as if I made a quick, hard tap on the accelerator just as it begins to fire - the engine roars and then settles right back down.
Haven't noticed any problems/noises with the AC...
Gary M.
2002 F250 SD, SC, SB, 4x4, 6.8L v10, 3.73LS, 4spd Auto, Reverse Aid Sensor, Class V Hitch, Offroad package, Manual Hubs, 40/20/40 Bench Seat, Towing Package, Camper Package, Lariat, White, Putco Locker Side Rails, Mud Flaps, K&N Filter, Vent Visors...
Haven't noticed any problems/noises with the AC...
Gary M.
2002 F250 SD, SC, SB, 4x4, 6.8L v10, 3.73LS, 4spd Auto, Reverse Aid Sensor, Class V Hitch, Offroad package, Manual Hubs, 40/20/40 Bench Seat, Towing Package, Camper Package, Lariat, White, Putco Locker Side Rails, Mud Flaps, K&N Filter, Vent Visors...
Fleet Mechanic
Joined: Nov 2001
Posts: 1,553
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From: Corpus Christi, TX
another engine noise
[updated:LAST EDITED ON 26-Apr-02 AT 08:30 PM (EST)]If I remember correctly, when you start the truck cold, the computer bumps the idle speed up to warm the engine up, but will drop if you touch the brakes, shift into drive (dunno about manual trannies), or if you touch the gas. The thumping is a door in the AC system moving, mine has done it since day one, pretty darn loud and a bit unsettling at first. I think the AC system loses it's vaccum, and the door either opens or closes with no vac, but as soon as you start the engine and vac pressure builds *THUMP*, it's back to where it should be. If it bothers you, turn your AC to OFF when you turn off the truck, the thumping only happens when it's turned off with the AC still on. If anyone wants to elaborate on this, or correct, go ahead!! My memory is kinda fuzzy from all the V-10 power 
Posting Guru
Joined: Mar 2002
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another engine noise
[updated:LAST EDITED ON 26-Apr-02 AT 08:46 PM (EST)]> When starting the truck cold it makes a roaring noise for a
>couple of seconds I have been told that this could be the
>fan also after turning on the air it makes a very loud thump
>has anyone else experienced these problems?
I have experienced these symptoms.The fan noise goes away shortly after takeoff when cold.Every Ford truck that I have owned in the past 10 years has done this,it's normal.If and when the truck is hot,like when towing,the fan makes the same noise.We just don't hear it because of engine,road,and wind noise.It's just the fan moving air.Let's just say when it's cold the fan needs to see some rpms before the clutch lets go of it.
The ac compressor on my 96 will thump sometimes when it first comes on.I attribute this to the fact that it sits quite a bit between uses,so I haven't been concerned about it.
Hope this helps.
>couple of seconds I have been told that this could be the
>fan also after turning on the air it makes a very loud thump
>has anyone else experienced these problems?
I have experienced these symptoms.The fan noise goes away shortly after takeoff when cold.Every Ford truck that I have owned in the past 10 years has done this,it's normal.If and when the truck is hot,like when towing,the fan makes the same noise.We just don't hear it because of engine,road,and wind noise.It's just the fan moving air.Let's just say when it's cold the fan needs to see some rpms before the clutch lets go of it.
The ac compressor on my 96 will thump sometimes when it first comes on.I attribute this to the fact that it sits quite a bit between uses,so I haven't been concerned about it.
Hope this helps.
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
another engine noise
This actually has a name. It is called CASS or Compressor Anti-Slugging Strategy.
It is to prevent accumulation of liquid refrigerant in the compressor. The PCM will tell the compressor to kick in every so often.
If your compressor engagement is loud all the time then I would suggest you check the air gap. That is the space between the A/C clutch hub and the A/C clutch pulley. Mine is not large enough. I'm calling to make an appointment to have spacers put in. I can hear it engage when ever I am idling. Sounds like someone is hitting the frame with a rubber mallet.
The air gap should be between .35mm& .75mm.
It is to prevent accumulation of liquid refrigerant in the compressor. The PCM will tell the compressor to kick in every so often.
If your compressor engagement is loud all the time then I would suggest you check the air gap. That is the space between the A/C clutch hub and the A/C clutch pulley. Mine is not large enough. I'm calling to make an appointment to have spacers put in. I can hear it engage when ever I am idling. Sounds like someone is hitting the frame with a rubber mallet.
The air gap should be between .35mm& .75mm.
Cross-Country
Joined: Jan 2002
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From: USA
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another engine noise
I have the same momentary "roar" from the engine upon start-up. Scared the crap out of me the first time it happened. It sounded like air intake noise with the throttle all the way open for about 1.5 seconds and then stopped. It seems to happen more often when the truck has not been started for a couple of days. I also have the thump in or around the passenger firewall - floorboard area and have determined it's A/C oriented as it doesn't happen when the air controls are left in the "off" position before stopping the engine.
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another engine noise
The A/C door does make a pretty good thump a few seconds after startup on my 02.:-staun My 96 doesn't do this at all.I wonder why the newer SD trucks do this .I'm sure it's normal though .
.I'm sure it's normal though .
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Joined: Apr 2002
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From: Seffner/Tampa Florida
another engine noise
Gary's 99 V10
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=4669&.jpg
I have 37000 miles on my 99, and every once in a wile I have the sam "Thump" when turning on thi AC. It does it if I turn on AC just at the same time I start up. Not all the time just some time. Seems to be ok. Sounds like the compresor in froze up for just a sec, like lhe clutch is stuck. But that only last for a split sec.
:-X23
Gary E K
garyekuy(No Email Addresses In Posts!)
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=4669&.jpg
I have 37000 miles on my 99, and every once in a wile I have the sam "Thump" when turning on thi AC. It does it if I turn on AC just at the same time I start up. Not all the time just some time. Seems to be ok. Sounds like the compresor in froze up for just a sec, like lhe clutch is stuck. But that only last for a split sec.
:-X23
Gary E K
garyekuy(No Email Addresses In Posts!)
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