Replacing Blue Coolant Temp Sensor Mk2 Golf GTI 8v

[Volkswag]

My car has been running rich and idling poorly for a while now and after a new Air Flow Meter and new spark plug leads, the mechanic has told me it might be the coolant temp sensor. This does make sense to me as the temperature gauge takes along time to show the car is heating up, and even then it never gets over 1/4 up the dial.

I am about to order a new coolant temp sensor ( VW MK2 Golf GTI Genuine 125 Deg Blue Temp Sensor Part 025906041A Brand New | eBay ) and I was just wondering if it is hard or risky to replace it my self. The Ebay listing gives instructions for replacing, and that the engine needs to be reved to 3000 three times to reset the ECU before the new sensor is plugged in.

Is there anything else that I need to know, and is there anything that can go wrong when replacing the part that I should watch out for?

Thanks!

[ryana89]

Evening, you're on the right track.

Your MK2 has 2 coolant temp sensors,
1 is BLACK and tells the gauge in your dash what to do (these fail and cause weird/no needle movement)
1 is BLUE and tells the ECU info about coolant temp (these are a common failure too and cause weird running)


Pull the retaining clip off, old out new in, and make sure the rubber o-ring is there.

And follow whatever method it says for the 3000rpm business.

[ryana89]

Have a read of this if you have spare time,

The uber DIGIFANT thread

[h100vw]

Have a read of this if you have spare time,

The uber DIGIFANT thread

If it's not going over a 1/4, is the thermostat stuck open? Running cold would account for poor fuel consumption.

Swap the connectors over on the blue and black sensors, see if the gauge moves.

Gavin

[RedMk2Gti]

If it's not going over a 1/4, is the thermostat stuck open?

+1, I rarely hear the black sensor go wrong.

[ryana89]

Mine didn't when I bought the car...

[Volkswag]

I changed the blue sensor about a week ago and it still seems to be using the same amount of fuel and the temp still never goes over a quarter on the gauge. I guess that means I'll look into getting a new thermostat.