1.8T AWT 2001 Coolant problem and temperature sensor recall

[Entropy]

My 1.8T has not been getting up to temperature and I suspect a problem with the coolant temperature sensor as the electric fan is always on. So I intended to replace it and take the opportunity to replace the coolant as it looks milky which I understand may indicate an oil leak in the oil cooler. However on closer look in the expansion tank, there's also a red precipitate coating the plastic. I have previously topped up the coolant with Texaco Havoline Extended Life Antifreeze Coolant which claims to meet the G12 standard.

I'd be grateful for any advice on the matter - if it's not the Havoline reacting with the existing VW G12 coolant, how can I check if the oil cooler is leaking? Also, I see no other option but to try and flush the system before replacing with new coolant and would appreciate suggestions on how best to do this and try and remove as much of the gunk as possible.

As for the coolant temperature sensor, it looks like this was the subject of a notice to extend the Emissions Control Systems Warranty in the USA - http://forums.vwvortex.com/showthread.php?3701577 - does anyone know if this notice has been sent out to UK owners?

[Crasher]

It could be the sensor in the radiator lower outlet, not the one in the head. If the oil cooler fails, it fills the expansion tank with a thick sludge that looks like milky chocolate.

I have not heard about a recall for the temp sender on the 3B in Europe but then again the Yanks whinge so much that I am surprised they don’t ask for a recall when the fuel tank runs low.

[Entropy]

Cheers Crasher - yes your right, it is more likely the radiator fan switch which I have planned to change but whilst I am at it, I intend to change the coolant temperature sensor and the thermostat - I've tried today to unbolt the thermostat coolant hose connector - top bolt no problem but sods law the bottom is more difficult to get at because of the alternator and my attempts so far have failed - I need a longer 5mm hex key so that I can get some purchase.

The gunk in the expansion tank seems to have coated the inside but there was also a small amount of creamy sludge as well as the milky coolant - I've removed the tank to clean it. The red gunk has also coated the inside of the hose connecting to the expansion tank so I suspect it has done the same to all other parts so I reckon a thorough flush is a must.

I think I should be able to check the oil cooler for leaks if I take it off and pressure test it with air. If the problem is not due to oil contamination then I can only assume it must be due to the Havoline antifreeze - if so I hope this is a cautionary tail for others to take note of as I will only use genuine VW coolant in future.

As for the recall, a few years ago when I was having problems with a main dealer (to remove the front grill for a timing belt replacement a service engineer literally chiselled off a hex bolt/washer and I had to have the front wing repaired and resprayed!), I had a warning light come on and had it fixed gratis as part of the repairs and good will - the service manager mentioned it was a temperature sensor "difficult to get at" - I reckon he was referring to the coolant temp sensor and if so how many others have failed in UK 1.8Ts? I wonder if in the US they have a different Emissions Control Systems Warranty that doesn't apply in Europe?

[Crasher]

How many have failed on 1.8T’s? It is not exclusive to that model. The switch used on yours, 06A 906 381 A is so unreliable that we keep 20 in stock and they fail on all sorts of VAG cars and it is not just that version either, it is probably the most single common reason for the engine malfunction light coming on, on all VAG vehicles.

[Entropy]

That's reassuring especially as it's a pain to get at - by the way, I thought the part number was 059 919 501 A

[Crasher]

It is, I had had far too much red wine by then and was going from memory, 06A 906 381 A doesn’t even exist!