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2000 4.2 Overheating at Idle -- Fan Problem?

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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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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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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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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, 06:18 PM   #11
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STOP RUNNING THE CAR TILL IT PEGGS OVERHEATING!!!!!! seriously these are aluminum heads that can warp, ask me how i know!
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Old 07-06-2010, 06:29 PM   #12
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STOP RUNNING THE CAR TILL IT PEGGS OVERHEATING!!!!!! seriously these are aluminum heads that can warp, ask me how i know!
Understood -- thanks for the admonition.
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Old 07-06-2010, 06:46 PM   #13
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just dont want your fan issue to turn into a head gasket issue
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Old 07-06-2010, 06:57 PM   #14
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just dont want your fan issue to turn into a head gasket issue
Yah, I hear that. I've also been there and done that on another car (my '93 Taurus) about 10 years ago and it wasn't much fun.
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Old 07-06-2010, 09:02 PM   #15
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Quote:
Originally Posted by spoon2000 View Post
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.
Should do one every 3 years or 36K at least with the old green stuff. Might could squeeze 5/60K out of the pink stuff. Mine with just a clutch fan takes a while to get warm and if I rev it up in traffic it cools back down. Just thinking might have some gunk in your radiator core.

You might be right with the part number, I have a old scan from a parts book and that is the only fan loaded.
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Old 07-07-2010, 08:26 AM   #16
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DO NOT USE THE GREEN STUFF!!!! it will damage the aluminum components!!! seriously stick with g12 or g12+ DO NOT use the green stuff... only pink or purple!!!
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Old 07-07-2010, 08:40 AM   #17
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DO NOT USE THE GREEN STUFF!!!! it will damage the aluminum components!!! seriously stick with g12 or g12+ DO NOT use the green stuff... only pink or purple!!!
Agreed. The Audi part number for a 1.5 litre bottle of the pink stuff is ZVW 237 G12. It's Pentosin Lifetime Antifreeze G001200. It should be mixed 1:1 with water (preferably distilled or otherwise filtered) for greatest protection against freezing and overheating. Available at many European car dealers (VW, Audi, BMW, MB, Jag, etc.) or from any number of parts places on the web (ECS Tuning, Blauparts, German Auto Parts, Amazon, etc.).
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Old 07-07-2010, 09:59 AM   #18
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A couple updates for the benefit of the collective wisdom:

I discovered that both the A/C fan in front of the radiator and the aux fan behind the radiator are VERY easily removed. To get the aux fan out, you remove one screw and then twist the whole assembly and lift it out. To get the A/C fan out, you remove two Torx screws plus one bolt at the bottom (accessible through the grille below the bumper), slide the fan to the center of the car (where there's slightly more room between the bumper and the A/C condenser and radiator) and then lift the whole assembly out. Took less than 5 minutes to get each fan out having no idea what I was doing when I started.

I also discovered that it's possible to cross plug the fans into each other's spot on the wiring harness under the black plastic shield next to the power steering pump (the aux fan has black connectors, and the A/C fan has brown connectors). The plugs are designed with some minor differences in the way the plastic is formed to make them more idiot proof, but they'll mate with each other if you use some minor creative persuasion on the plugs. Both harnesses output approximately 11 volts.

I am PRETTY sure the motors on both fans are the same, but that the blades and the mounting arms on each fan support are slightly different. I don't plan to switch the blades to find out. For those who may want to undertake such an adventure, be advised that the blades are attached with reverse-threaded nuts. I think the difference in blades is what accounts for the howling noise the A/C fan makes when running.

The bottom line is that my aux fan does not work consistently when plugged into either harness, whereas my A/C fan works 100% when plugged into either harness. So my presumption at this point is that my aux fan is bad and not the controller or wiring, etc.

My bad aux fan with part number 4B3 959 455 is identical to part 8D0 959 455 that my local VW dealership carries (for $400). However, the part the VW dealer stocks is available from RockAuto.com as 8D0 959 455R (note the R on the end) for $75, so I'll be ordering it from there. See http://www.rockauto.com/catalog/moreinfo.php?pk=952469 for more info. You can also order it from ECS Tuning for something like $110, plus there are a couple fans on eBay for $65 if you want to fiddle around with that route.

Last edited by spoon2000; 07-07-2010 at 12:47 PM.
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Old 07-07-2010, 10:50 AM   #19
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This is great info! I think my A6 has the same problem. It has gotten pretty warm at idle. I've personally witnessed 5 or 6 VW cooling fans fail, so I suspect the construction and reliability of these is probably similar. Going to dig into them this evening.
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Old 07-07-2010, 11:27 AM   #20
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and you wanted to get rid of the mechanical fan!?
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