Engine Coolant Temp Sensor

[clarky_two]

I have been getting mysterious spouts of my passat b5 130 over reving when ticking over, she goes up by 300rpm for a few seconds then drops back down to normal idle rpm.

i just bought the shareware VAGCOM and it comes up with " engine coolant temp sensor g62, open or short to plus, p1256-35-10 intermittent.

Can anyone tell me if this might be the cause? Or even better the solution?

[adamss24]

Replace it with a new one. They fail internally and will trick/confuse the ECU so it will retard timing and even inject more fuel as it thinks the ambient temperature is low and sometimes will lead to hard start on a cold day. I suppose you could clear the fault and take it for a drive to see if it returns. If the code pops again, replace it as it cost betwen 15-25 from most motor factors like GSF, ECP or dealer...

[producedapples]

If you do it yourself, buy the new o-ring too, but when you do it, make sure the engine isnt hot else youl get a shot of really hot coolant in ya face!! take about 3 mins to do too

[turbine2]

I had that on an old Audi once, exact same problem caused by the exact same thing.

[clarky_two]

OK I have now purchased the sensor, and took a quick look under the bonnet today. I found several sensors which could be the right one, but I am not 100% sure and I dont have a Haynes manual. A blue one down by the passenger side coming off the side of the rad, or a not sure what colour off the top of the engine.

Can someone point me in the right direction. I have read on the internet that its on the drivers side coming of the top of the head gasket. I have also read that it requires a full change of coolant and bleed the system. Found some pics but its from an audi A4 are they similar?

I have a passat B5 130tdi.

Cheers