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Fans running high, temp low all the time

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pacificblue View Drop Down
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  Quote pacificblue Quote  Post ReplyReply Direct Link To This Post Topic: Fans running high, temp low all the time
    Posted: 07-Mar-2017 at 03:13
VW Passat '03 W8 - 230,000km
The radiator fans run at high speed even when the car idling. Temperature gauge doesn't stay at 190F as usual - instead it stays around 120F.

cold start and fans start running at very high speed almost right away (10-15 seconds after start).
Both fans and they both run fast and pretty loud.

No CEL, Engine light is not on.
Started reading forums and people say different things like replacing:
temperature sensor, fan control module, fan relay switch, water pump and thermostat.

Any insights? I searched the forums here and didn't find any related posts



.
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JayTheSnork View Drop Down
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  Quote JayTheSnork Quote  Post ReplyReply Direct Link To This Post Posted: 07-Mar-2017 at 04:32
it's the thermostat, I bet. have you checked for any codes?

here's a link to my very similar problem here: http://www.w8forum.dk/forum_posts.asp?TID=5514&title=cel-and-tons-of-codes

and here's a link to a similar discussion on PW: http://www.passatworld.com/forums/b5-garage/517730-04-w8-cel-tons-codes.html

bottom line - when my t-stat went south, it took out a relay and blew a fuse. I got a CEL because of it... but your mileage may vary. I can help talk you thru troubleshooting this one if you can bear with me.
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  Quote unimogjohn Quote  Post ReplyReply Direct Link To This Post Posted: 08-Mar-2017 at 01:38
Pacificblue, my w8 wagon had the same problem. Replaced both temperature sensors and everything was fixed. The sensors are cheap, not hard to replace, but requires some crazy finger movement to get them in, especially the rear. The front is easy.
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  Quote unimogjohn Quote  Post ReplyReply Direct Link To This Post Posted: 08-Mar-2017 at 01:41
go to here for instructions. After doing it once, you can then do it in a quarter of the time.

http://www.w8forum.dk/forum_posts.asp?TID=896&title=diy--replacing-coolant-temp-sensors
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JayTheSnork View Drop Down
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  Quote JayTheSnork Quote  Post ReplyReply Direct Link To This Post Posted: 08-Mar-2017 at 02:14
the front temp sensor will throw a CEL. been there, done that.
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  Quote pacificblue Quote  Post ReplyReply Direct Link To This Post Posted: 08-Mar-2017 at 03:19
Thank you both
I'll give it a go and let you know
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  Quote unimogjohn Quote  Post ReplyReply Direct Link To This Post Posted: 09-Mar-2017 at 01:51
Don't worry about losing fluid when you remove the sensors. Only a couple of tablespoons come out.

I removed the back sensor from the right side of the engine. The sensor is down a couple of inches. I removed a couple of hoses to get my finger in there. I think I also used a long wood dowel to get it to seat. I also put some lubrication on the O rings to get them to slide in easier. Remember to make sure you get the old O rings out.
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  Quote pacificblue Quote  Post ReplyReply Direct Link To This Post Posted: 09-Mar-2017 at 16:52
sensors done, fan ran normally for the day and back doing the same problem

Im thinking either the electric thermostat

Is there a primary or secondary fan control module I can also check out?
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JayTheSnork View Drop Down
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  Quote JayTheSnork Quote  Post ReplyReply Direct Link To This Post Posted: 09-Mar-2017 at 18:05
Have you had it scanned for codes yet? As I stated before, I know the front sensor will throw a code and a CEL.
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  Quote JayTheSnork Quote  Post ReplyReply Direct Link To This Post Posted: 09-Mar-2017 at 18:06
Btw, the t-stat isn't cheap. Around $230 USD...
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