A4 2.5 TDI quattro Sport - Fuel economy has dipped ?

[mjsork]

Hi
I am wondering if anyone has had a similar problem. My 2003 A4 2.5 tdi quattro sport fuel economy has taken a serious dip. The engine appears to be fine with no change in performance. The only thing I have noticed is that after a long drive the temperature gauge is not running at the normal 90degc, instead it is only reaching approx 60-70degc. I am therefore thinking that the thermostat is broken and I am hoping that the fact the engine is not reaching its normal operating temperature is affecting the ECU and making it drink more fuel.

Does this sound about right, if so how easy is it to change the thermostat?

[kite]

It could be the coolant temp sensor broken, which is easier to change.
The front of the car has to come off to change the stat, also a good time to change the cambelt and waterpump while the engine is in bits...

[burkey1]

While driving, have you the usual warm air coming through the vents when the heaters are at high,

If not it will most likely be the stat..

[mjsork]

Hi Guys,

The air from the vents was hot and the temp gauge hadn't even risen of the 50degc mark.

Lets hope it is the coolant temp sensor thats broke as you guys suggested.

A friend told me that there are two sensors, a green and a blue one, is that correct. if so which one do I need to change to sort out the temp gauge reading ?

[SWARCUP]

you will only have 1 temp sensor, this is green and sits under the engine cover on the top of the engine, Mine is doing the same and i changed this to no avail. Mine is booked in this saturday for the works, including cambelt and tensioners including the hydraulic one, diesel pump belt and tensioner,serpentine belt and tensioner, thermostat,water pump and 5 litres of new g12 antifreeze, full diagnostic and vag-com setting for the diesel pump. All this for a £25 thermostat. Aside from this though im still returning around 35 per gallon with a knackered thermostat. If you change the temp sender and there is no change i would first go for a vag-com scan as there are a lot of bits that may not be working correctly that may give you poor performance. Maf is one, this not only measures the amount of air going in but also the temp of the air, if this is off then it will be overfueling. Scan it and you will be closer to knowing. Keep us posted

[mjsork]

RIght Guys,

I went ahead and changed the coolant temperature sensor ( the green one) today and hey presto the temp gauge is now reading 90degc as it should.

It is only an year since I changed it, and last time I fitted a cheap replacement from Ebay. This time I bought genuine Audi. Guess it proves that cheap ain't always best.

Cheers for the help guys.

[SWARCUP]

nice1 thats saved a small fortune