They are bit of a sod to do, as on the gti there is an oil sensor and multiplug in the way (which is a bugger to get off!) Its on the side of the cylinder head near the coil pack, should be a 4-pin plug onto a green sensor. You pull the plastic 'u' clamp out, and the sensor will just pull out of the housing. You will lose some coolant as its part of the thermostat housing, so get some to top up again. Also make sure you get the o-ring too, part numbers as follows: Sensor (4 pin green) - 059 919 501 A (£35 ish) O-Ring - N 903 168 02 (£1 ish) Coolant (G13) - G 013 A8 JM1 (£10.36 inc vat!) Not sure 100% on prices as i'm not at my usual workplace today, only price I definitely know is the coolant!!!
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