A4 (B5 Platform) Discussion Discussion forum for the B5 Audi A4 produced from 1995-2001 B5 FAQ

going engine temp sensor?

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Old Nov 11, 2008 | 11:39 AM
  #1  
chris w/ a b5 1.8t's Avatar
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Default going engine temp sensor?

I changed my thermostat when doing the tb about 25k ago, so hopefully its not that...

Ive noticed that my temp gauge isnt reading 1/2 like it always used to for the last 2 months or so. It seems to fluctuate from normal to just a knotch under normal.

It's never gone above normal which I guess its good, but its not registering normal temp.

Heat is hot, coolant level is good, no codes.

Engine Temp Sensor? I even got a recall notice on it a few months ago covering to 100k, should I even bother taking it to the stealership for that or will they tell me to go pound sand since its modified.

Or, could the thermostat be going with less than 25k on it...?
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Old Nov 11, 2008 | 11:41 AM
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coolant temp sensor... either the one on your lower rad hose or the one on the back of the head
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Old Nov 11, 2008 | 11:43 AM
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chris w/ a b5 1.8t's Avatar
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any way to confirm which it is? or parts cheap enough to just change both
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Old Nov 11, 2008 | 11:44 AM
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I know the one in the back of the head is like 12 bucks
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Old Nov 11, 2008 | 11:45 AM
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Default they are cheap enough to change both... i wonder if vag would show anything

hmmm...

the back sensor is a bitch behind the head.. buy a new plastic u clip.

the one on the lower rad hose = not a big deal

just both of them are going to cause coolant to pour out

Oh .. if you're changing the one on the back of your head... change out the whole flange. It's worthwhile
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Old Nov 11, 2008 | 11:45 AM
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Default sounds like thermostat to me. but i'm dumb.

however i had the same symptoms - replaced the ECT sensor, no change. Replaced the thermostat, fixed.<ul><li><a href="https://forums.audiworld.com/a4/msgs/2670327.phtml">my prev. posts</a></li></ul>
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Old Nov 11, 2008 | 11:46 AM
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Default see i actually agree with you. Problem is that he changed it 25k ago

so... I'd like to rule it out

but

then again... parts sometimes fail early

oh well sensors are cheap and easier. If they don't fix it. Then it's temp stat.

there has to be a smarter way to attack this though, less trial and error
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Old Nov 11, 2008 | 11:48 AM
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chris w/ a b5 1.8t's Avatar
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Default had vag plugged in this weekend and nothing

thanks for the tips!
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Old Nov 11, 2008 | 11:50 AM
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Default I had this problem after I changed out the head temp sensor.

Before that it would vary widely. Now its just 1 tick or less. It never bothered really since it was way worse before. Maybe I should change the other one.
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Old Nov 11, 2008 | 01:30 PM
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Default if it looks like a duck, and quacks like a duck...

But like you say, cheap enough to try both, and I too would like to believe parts are more reliable than this instance would indicate.

I always thought the 'real' ECT sensor failures had very erratic temp readings (too hot, down to immediately stone cold, back up, etc) as symptoms.
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