^{My economy really suffers the first 5 miles or so in the morning, even moreso in winter..  I was wondering if the viscous fan could be disabled (maybe just remove the blades assembly), leaving the electric fan and airflow from vehicle motion to provide enough cooling - anyone tried this?}

The viscous-coupled fan does nothing until the bimetal strip is heated by the radiator. If you're brave, you can hold the blades stationary with the engine running - it's just the drag in the fluid which makes it turn, but the coupling slips at a low speed with a cold fan.

 

The real problem with VAG engines is thermostats - they can't or won't make ones which last and they all fail by opening a bit early and then staying open for too long, resulting in low coolant temperature and a slow warm up. The dashboard thermometer is useless as it is "sanitised" by the instrument CPU to stay in mid position over a wide range. Real-life fluctuations are not allowed in Wolfsburg - drivers must see perfect engine functioning.

 

VAG thermostats are generally useless by about 80k miles and are best changed with the water pump. You can then push the thermostat out through the water pump hole, which avoids breaking off the retaining tabs in the thermostat elbow - which always happens if you pull it. Always use OE thermostats and a new "O" ring. Aftermarket substitutes are useless and don't fit the retaining tabs.

 

rotodiesel.

Interesting.  123K miles on mine now, so I guess it may be goosed by now - logging with VCDS might show it?  Always rock-steady at 90 once it warms up.

 

Shame that my belt & water pump aren't due for 30,000 miles...

Have you disabled/blocked your EGR by any chance? If yes, the simplest way to warm up engine normally/quicker is to re-enable it and make sure the valve is working properly.

 

Without EGR, the engine is constantly cooled with full fill of cold air at idle. Years ago, I had set EGR valve to lowest via VCDS on my Octy1 (non PD), and subsequently I could not warm the engine up at all in town, only on motorway.

Edited 4 September, 201411 yr by dieselV6

No, EGR is fitted and should be working I guess - it was replaced at around 70K at main dealer (warranty) as it was spraying a bit of oil around the engine.

 

So on the subject of the viscous fan, if I stop the pulley with my hand (engine off and cold), I should be able to turn the blades relative to the pulley with ease?  

 

I've not checked, but I was pretty certain when I was doing all the alternator stuff that the blades seemed to be pretty much locked to the pulley's rotation.  I wonder if the viscous fan coupling has failed and locked up, so my viscous fan is always at full tilt?

Could be, coupling is not hard to replace.

I will give it a look later.  It will be a little bit of a shame as it has to go to service position if I have to get the coupling out.  Not difficult, just time I'm short of!