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Old 05-20-2012, 08:20 AM   #1
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Engine Roars When Hot and A/C

My 04 Wrangler with 4.0 auto has always done this but I wonder why. Only after some hot highway driving with cold a/c blasting do I notice this. When taking off from a stop the engine makes a noticeably louder roaring sound and seems to be working harder to accelerate. My wife even asks, "Why does it sound like that?". The temp is fine but at its highest point after sustained interstate speeds and stop and go St Louis traffic. The roaring eventually goes away and it doesn't always do it but I can't figure out exactly what's making the sound increase. Anybody know why? Any similar experiences? I hope I explained myself well.
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Old 05-20-2012, 08:37 AM   #2
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The roar that you are hearing is coming from the fan. When the engine is hot enough the fan clutch engages to help cool the engine. after the engine cools down the clutch disengages and the fan spins slower so you no longer hear the roar.

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Old 05-20-2012, 08:53 AM   #3
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Yep thats the fan clutch doing it's job right there...,
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Old 05-20-2012, 09:03 AM   #4
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With the engine cold (and the key out of the ignition) you should be able to spin the fan freely by hand.

If you cant, the clutch is frozen.

Running with a frozen fan clutch wont hurt ya...but will erode your fuel economy a bit.

Replacing it is fairly cheap and easy.
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Old 05-20-2012, 09:08 AM   #5
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Thanks guys. Makes sense and I feel much better. We're taking it to Yellowstone in a couple of weeks so I'm getting everything in order.
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Old 05-20-2012, 05:36 PM   #6
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Sounds like a beautiful trip.
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2005 Black Suzuki C50T (ours)
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Old 05-20-2012, 06:15 PM   #7
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That's beautiful country! I haven't' been back since 88 when we were fighting the fire.

QUOTE="JeepnJim"]Thanks guys. Makes sense and I feel much better. We're taking it to Yellowstone in a couple of weeks so I'm getting everything in order.[/QUOTE]

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