Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises

Honest John Back Room » Technical matters
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Sun 3 Feb 2013 14:40
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - csgmart

During my 50 mile commute to work I am finding that the temp gauge on the Polo rises and falls regularly during the journey. If I stick at 70 on the motorway this equates to 3000 rpm and at this speed the needle drops from normal to about 1/4 temp and then raises again.

I suspect the sender may be faulty (and I'm also suspicious that I'm getting a poor fuel economy too) and this could be causing the needle to rise and fall.

The car starts and drives perfectly and the header tank is on the full mark and has not dropped in the 6+months I've owned the car.

Is there a temperature sender and if so where will it be located? Could a faulty sender also cause the engine to run too rich?

Your suggestions / thoughts are appreciated.

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Sun 3 Feb 2013 15:12
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - elekie&a/c doctor
temp sensor failure is probably the most common issue with vag engines,causing running and gauge faults.It is usually a green plastic 4pin sensor located in the coolant pipe ,near the thermostat.hth
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Sun 3 Feb 2013 22:23
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - VR6

Normally an 'erratic' temperature gauge (i.e it shoots up and down randomly) points to a failed temperature sender/sensor as stated above. However, if you're saying that the temperature drops steadily with speed then that would point to a failing thermostat.

Don't buy a cheap temp sender from ebay, as i've heard very bad reviews.

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Sun 3 Feb 2013 23:29
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - Crasher

I suspect that the thermostat is either faulty or has been removed altogether in an attempt to cure overheating which is caused when the reaction pin location for the thermostat blows through and people consistently miss this fault and end up binning the thermostat but I have seen these thermostats fail wide open and cause this fault. A new thermostat and cover are tricky to fit so a new complete head side moulding is a better idea and these often come complete with a new temperature sender anyway. You may have rich running lambda codes stored on the ECU because of this which can explain your poor fuel economy.

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Mon 4 Feb 2013 03:03
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - 1litregolfeater

Yes, could be as simple as a worn out / sticky themostat.

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Mon 4 Feb 2013 07:42
Volkswagen Polo III - 2001 1.4 Petrol - Temp gauge drops and raises - csgmart

Thanks for the responses so far.

I'm not 100% convinced I'm getting poor fuel economy but I struggle to get 400 miles on a full tank and my previous Polo (1996 vintage) seemed to go a bit further than this on a tank.

The car does start well and within a mile the gauge registers heat.

At 70 mph the needle drops and rises - at higher speeds the needle tends to stay on normal which seems to suggest either a faulty sender or a failed/missing thermostat.

Perhaps the safest option is to go with a complete unit as recommended.

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