tegwin
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| posted on 26/11/12 at 04:54 PM |
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Tin top cooling on overrun
Have a curious issue with my 2001 polo 1.6 16V.
Normally the temp gauge sits rock solid at 90 degrees all day long and never moves...
I noticed on a very long downhill section where I had my foot totally off the loud pedal for around 40 seconds (70mph) that the temperature was slowly
dropping, maybe dropped by 5 degrees.
As soon as I opened the throttle again at the bottom of the hill the temp went back up to 90 and stayed there...
Happened a few times over the weekend and I had not noticed it before. Any idea what it could be?
(I know this engine is prone to faulty temp senders but that is usually erratic randomness, not consistent irregularity on overrun!)
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coyoteboy
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| posted on 26/11/12 at 05:59 PM |
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40s of overrun is a reasonable time without heat input to the coolant and with full heat output from the rad, perfectly possible the temp sensor is
that responsive. That said, how accurate is the sensor and display that you can be sure it's 5 degrees and not 1 or 2. Or 10.
Datalogs from my tintop show it drops from 105 to 95 degrees in about 3 minutes, between full blast and general cruising.
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garybee
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| posted on 26/11/12 at 08:55 PM |
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Doesn't sound unreasonable to me either. I would keep a slightly closer eye on it than normal over the next few weeks though as it may just be
the very start of a thermostat failing in the open position.
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tegwin
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| posted on 26/11/12 at 09:07 PM |
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Just strange that it has never happened before... Have had the car for nearly 6 years and I do an instrument scan every few mins so I do notice any
irregularities (a weird habit carried over from flying) Tend to check engine temp and warning lights before I ask the engine for power for an
overtake..
Will plug in Vag-scope at some point and see what the actual data looks like. I know it has had coolant flush 2 years ago when the cambelt was done so
it should be fairly clean inside...
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coyoteboy
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| posted on 27/11/12 at 09:24 AM |
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If it's newly started I suppose you could have a sticky stat, will tend to lag open longer than it should, allowing over-cooling.
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tegwin
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| posted on 27/11/12 at 10:36 AM |
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Hmm, It's due a service. Might pop out the stat and have a look at it 
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PSpirine
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| posted on 27/11/12 at 12:07 PM |
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Every VAG car I've had needed a thermostat changing at some point. One of them I couldn't see that it was sticking open even when I did a
bench test.
If it's easy to get to, I'd change it at the next service. Genuine parts are about £15 I think.
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