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My Diesel Fabia gauge goes to overheat and the Temp warning goes ding and lights up. After a minute or so all is well and the gauge goes back to the centre, then it happens again but the engine doesn't appear to be boiling. I would have expected the cooling fans to come on but they don't. The fuse is ok. Where are the coolant temp sensor and the fan switch and how can I test them. I do not think that I have an engine problem as the gauge sinks back to normal too soon. Please can anyone help?
Edited by Dynamic Dave on 16/04/2008 at 13:16
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On an ATD engine, it's in a plastic housing on the back of the head. Probably a four-wire sensor held with a clip.
You could have a thermostat issue or even be low on water.
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Thank you. The water level is fine, I did consider the thermostat. I am an old fashioned car mechanic and finding these things on a modern car is almost impossible. Do you know where the Fan switch is ?
Edited by Pugugly on 16/04/2008 at 16:43
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There may not be one; these days I'd hope - even on a Skoda - that temperature information was CAN networked between all the ECUs from the one sensor.
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"Even on a Skoda" - cheek, Screwloose, I've got a bigger one of these and the engine management is just VAG group standard for whatever the model year is.
Seriously though, a good place to look when you have eliminated the easy ones is the water pump. Dear old VAG use a plastic impeller which either breaks up or comes loose on its shaft. This gives the effect of poor circulation at high engine revs and will cause the engine to overheat very quickly. At lower speeds and idle, all is normal.
Metal impeller replacements are available from GSF. If this job has to be done, the cambelt can be done at the same time as it drives it.
Another VAG weight saving misfire I'm afraid. (Eliminating the pinion nose bearing on the early transverse engine starter motors was another one of their "bright ideas" which caused vehicle users a lot of grief at the time).
60 - 80 k miles is the usual grief point for these pumps.
659.
Edited by 659FBE on 16/04/2008 at 19:02
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Thanks guys, I'm working my way up to looking at it this weekend. Any other suggestions from anyone gratefully received. 659, the car's done just 60,000, is there any easy way to find out if the impeller is the culprit?
If I short out the coolant sensor will the fan(s) work or is it done only by the Fan switch (if fitted)? How can I eliminate these?
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If your car is almost due for a cambelt change, I would simply do it (there would be little "residual value" in your existing belt) and change the water pump at the same time.
If you want (quite reasonably) to take a more analytical approach, I would exonerate the thermostat by substitution. The water pump is speed but not engine load sensitive, so a possible test would be to disconnect the cooling fan(s?) for safety and then rev the engine hard in neutral for several minutes. If there is an appreciable temperature gradient across the radiator, the pump is not doing its job. Often, the impellers come loose on the shaft only when hot.
659.
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Shef
I woudn't try shorting any ECU sensor unless you like spending very large sums of money.....
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Well guys thanks but it's not the thermostat or temp sender, guess it has to be the pump. If I stay under 50 mph it behaves but over that it creeps up to the red and ding ding ding. Funny though after 1-2 mins the temp is down almost to the regular 1/2 way point. It seems to cool off very quickly for water! I will do it and the timing belt at the same time, any nasties I should watch out for.
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Well guys thanks but it's not the thermostat or temp sender, guess it has to be the pump. If I stay under 50 mph it behaves but over that it creeps up to the red and ding ding ding. Funny though after 1-2 mins the temp is down almost to the regular 1/2 way point. It seems to cool off very quickly for water! I will do it and the timing belt at the same time, any nasties I should watch out for.
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Job done. Water pump plastic impeller spinning like a good'un while drive cog was still! Took a while but it was pretty easy, new tensioner was a bit fiddly as was getting out the lower half engine mount. Test drive showed the gauge rock steady on the line. Bits were £100 from GSF and Haynes manual £15.
Thanks for the steer 659 you were dead right. Pump has a plastic impeller from GSF.
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