Mk 4 Golf SDI 1.9 coolant temperature sensor change.

So the temperature gauge on the dash isn't registering at all but before that it was working intermittently. Seems like i need to change the coolant sensor. The proper way i suppose is to drain the system but that involves removing the under engine protector which i've not long done to change the oil. Some tutorials show to unclip the sensor without draining the system and quickly put the new sensor in. I can't get the wired connector off because the tab is between the sensor and the engine block. If i pull out the sensor and let the coolant out how much am i likely to lose? I'm thinking about putting some kind of plastic tray under the sensor to catch it but obviously the size of it depends on what's lost. Thanks in advance.

I changed mine many years ago and did not drain the coolant. Remove the sensor (be prepared for some coolant loss) and top up afterwards. Obviously, keep checking the level and release trapped air from expansion bottle afterwards.

Thanks, i've found a drain tap at the bottom of the radiator so i'm going to drain the system and change the thermostat, housing and temperature sensor all at once.

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Originally Posted by herby0001

I changed mine many years ago and did not drain the coolant. Remove the sensor (be prepared for some coolant loss) and top up afterwards. Obviously, keep checking the level and release trapped air from expansion bottle afterwards.

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