Thermostat on 2.5 TDI A6
 

Thermostat started sicking open on our A6. Most of the time OK, sometimes takes forever to warm up.

Changing it is front off and all belts off job. Belts need changing in 10-15k miles and I was going to do it next summer. Not sure what to do :

1. Leave it alone and hope it does not get worth and change everything next summer because weather is not all that good to do it outside although I might get a space in garage if they are not too busy.

2.Just change thermostat @£10 and £30 for timing tool rent and do the belts next summer. But do not fancy doing it twice.

3.Change the whole lot but looking @ over £400 for belts, rollers, tensioners, damper, water pump, thermostat, coolant. After some unexpected expenses I do not have spare £400 available and this would mean no winter tyres this year.

I would go for option 1.5 -
Leave it alone and hope it does not get worse - if it DOES get worse then either Just change thermostat if finances not improved / poor weather or do the whole job if you can by then +++

The problem with that is that weather is not getting any better/warmer any time soon an I would rather do it now then in middle of January. If I can get into garage then not much of an issue. I guess if it happens in January garages will not be too busy as people will have less money to spend after Christmas and will be easier to get space to let me in. It should not be more then 4-5 hour job maybe 6 since I will be doing it for the first time on this engine.I think I will buy thermostat to have on standby and hope for the best. If it does get stuck open it will take long time to warm up and affect fuel economy but I can cover half of radiator to reduce cooling. As long as it does not get stuck closed.

The plan was also to get the intake pipe and manifolds off when doing belts and have them blasted by crushed nut shells to remove carbon build-up from EGR now that I have blanked it off and disabled in ECU. So that's an extra expense on top of it.

I would leave things till you're ready to do the belt and tensioner / rollers. The good thing is the thermostat is sticking open intermittently - not closed. So the inconvenience is more a car that's lukewarm through the cold winter months, and possibly a bit thirstier due to non-optimum operating temperature.

Unless you're likely to rack up 15,000 miles before the weather gets warmer, I'd leave well alone. My take on things.

One of my friends has the same issue on his 2.5Tdi.
It's been like this for probably a year now. It happened about 6 months after the belt change so he decided to wait until the next one instead of replacing. Apart from facing another winter of driving with a jacket on, he said the car has been fine.
It's got high miles (235k) so owes him nothing. Fuel economy hasn't suffered much. He still gets about 600 miles to the tank and going slightly off topic, he noticed if he leaves his roof bars on (proper Audi ones) he gets 500 miles to the tank!

Are You talking about the ones that run on either side of car or the ones you put across top of those?

I'd say he means the cross bars. The roof rails either side are permanent.

Sorry, meant to say it is a saloon so just cross bars.
He does the majority of his driving on the motorway.