Car's been showing some random temperatures of late, with a recent thermostat and water pump I decided to give this a go. These are part numbers and prices from TPS: 059919501A Temperature Sender £26.17 032121142 Retaining Spring £0.42 90316802 O ring £0.93 Plus 1.5L G12 £4.28 Pop the cover off and here is the sensor, I was quite pleased to see mine looked like it had been weeping, helped to convince me it was at fault: The little plastic locking spring can be eased out carefully so you don't drop it: I used pliers, as long as you've got a replacement you don't need it. But knowing my luck it would pop the timing belt off! It will just lift out then. It's best to unplug it before lifting it out to minimise coolant loss, but this is for demonstration - the little catch just levers up and it will pull out. You might not be able to do this in situ, I couldn't, hence the G12 above: I cleaned the plug up and sprayed some water dispersant in, and also wiped around the O ring seal. Don't forget to take the old O ring out if it doesn't come out with the sensor! Fit the sensor: Job's a good 'un: I ran the car at this point to make sure there were no leaks. Top up the G12 and you're done: Mine looked pretty grotty so I've no objections to the £38 spent.