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Old 07-06-2010, 01:41 PM   #1
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Default 2000 4.2 Overheating at Idle -- Fan Problem?

Our 2000 4.2 overheated the other day during stop and go driving in the 100 degree East Coast heat. When this happened, the A/C stopped blowing cold air. This problem has happened before during slow driving in extremely hot weather. Coolant level is fine, and the coolant temperature sensor near the rear of the engine was replaced within the past couple months. There are no OBD or VCDS fault codes stored in the car's computer.

I noticed that the electric fan on the driver's side behind the radiator (i.e not the one in front of the radiator that comes on with the A/C, and not the engine-belt-driven fan on the passenger's side behind the radiator) was not running when the car was saying it was overheated. I unplugged the harness connector for the fan and got 11 volts. Then I applied voltage via a wire from the cigarette lighter to the fan, but it didn't turn.

Am I overlooking anything that could be wrong other than the fan motor being shot? Is it common for these fans to croak? How much of a pain the rear is it to remove and reinstall this fan? Anybody know a part number?

Many thanks!
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Last edited by spoon2000; 07-08-2010 at 10:18 AM.
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Old 07-06-2010, 02:31 PM   #2
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yes electrical fans can and do die. you are the second one to complain of this. does your car AC work (colder) when your moving? if so the fan is the issue.
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Old 07-06-2010, 02:57 PM   #3
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We have a 2K4.2. It has overheated, once due to a faulty thermostat which pegged the meter...shut off, no damage, TB and thermostat and engine fan clutch job, spendy $$$. (Have to take off the TB so might as well put a new one on if the old one is over 50K miles. Tensioner, pulleys, and WP wait for scheduled TB replacement however.)

The second time it was the fan control module AND the fan. Another $1200 to the stealer.

So there are a couple of possibilities.
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Old 07-06-2010, 04:16 PM   #4
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Quote:
Originally Posted by 2.7Lturbo View Post
yes electrical fans can and do die. you are the second one to complain of this. does your car AC work (colder) when your moving? if so the fan is the issue.
Went out to the car again, and saw that about 3/4" of coolant had disappeared from the bottle since my last drive. Started the car and drove it again, and it overheated and the A/C started getting warmer within about 5 minutes of neighborhood driving. At that point, I took it onto limited access road and drove for 5-10 minutes at 60 MPH (with the hood in the unlatched position to generate more airflow to the engine). The temp gauge stayed just short of pegged, and the A/C got slightly cooler, but it certainly didn't blow cool air the way it did when I first left the house. When I got back home and let the car idle, the temperature gauge went all the way to hot, at which point I turned the engine off and raised the hood to allow air to circulate. The auxiliary fan was still not running.

Further thoughts?

Last edited by spoon2000; 07-06-2010 at 04:19 PM.
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Old 07-06-2010, 04:27 PM   #5
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Fan or control module might be dead. You can check the big fuse for it under the knee bolster in the drivers footwell (the panel with the owners manual pocket).

Or test the output on the module, unplug the brown plug by the power steering resivoir and check for 11-12 volts on the female side after you turn your a/c all the way one LO.
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Old 07-06-2010, 04:51 PM   #6
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Quote:
Originally Posted by JoeM View Post
Fan or control module might be dead. You can check the big fuse for it under the knee bolster in the drivers footwell (the panel with the owners manual pocket).

Or test the output on the module, unplug the brown plug by the power steering resivoir and check for 11-12 volts on the female side after you turn your a/c all the way one LO.
I'm getting around 11 volts coming out of the harness so I'm thinking I'll proceed with a fan replacement.

Is it really possible that having that fan non-operational would cause the car to overheat so quickly?
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Old 07-06-2010, 05:05 PM   #7
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these motors are shoe horned in there, Mine waits until the oil is up to temp before it get warm, is you clutch fan working at all?
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Old 07-06-2010, 05:27 PM   #8
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Quote:
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these motors are shoe horned in there, Mine waits until the oil is up to temp before it get warm, is you clutch fan working at all?
Yes, the clutch fan (i.e. the fan running off the serpentine belt) seems to be working fine.
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Old 07-06-2010, 05:33 PM   #9
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yea, at under 25mph there isn't much airflow to cool it off. Might want to try a coolant flush when you can.

Should be part number 4b3 959 457
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Old 07-06-2010, 05:58 PM   #10
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Quote:
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yea, at under 25mph there isn't much airflow to cool it off. Might want to try a coolant flush when you can.

Should be part number 4b3 959 457
Thanks, Joe! But isn't that the part number for the A/C condenser fan, i.e. the fan on the front of the radiator? I'm thinking that the part number for the aux fan I need is probably either
8D0 959 455P
8D0 959 455R or
VW3115105.

What would a coolant flush accomplish, given that the coolant is supposed to be good (can provide proper anti-boil, anti-freeze, and corrosion protection) for the lifetime of the car? I should point out as well that the coolant bottle fractured 5 years back or so, at which point I'm pretty sure most if not all the coolant was replaced.
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Old 07-06-2010, 05:58 PM
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2000, 2001, 42, a4, a6, ac, allroad, audi, bad, fan, idling, location, overheat, overheating, problem, problems, themostat


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