Waxing??

Could any of you kind people out there please explain to me what 'symptoms' our Volvo S70 Tdi would be displaying if suffering 'waxing' of the diesel??

In general, it would be bad starting as the diesel starts to solidify in very cold conditions and starts to block the fuel lines and filter. I know NOTHING about s70 diesels! But would imagine they'd have a diesel preheater?? Hope this explains something.

This used to be a problem when we had proper winters, but am I right in thinking that the formulation of diesel fuel is such now that it shouldn't happen? Jack

The traditional cure for waxing of diesel oil in the UK, before 'winter grade' diesel was produced, was to blend a little petrol with the diesel in the tank, not a lot, I think the truck drivers used to use about a 25 to 1 mix (or less), diesel to petrol. Your garage's instructions to drain the fuel tank also leads me to believe that they might think that you have some water in the tank (from condensation), and need to drain the tank to get rid of this. There must be a fuel filter and water trap on the fuel lines somewhere, clean and/or change these as appropriate.

Thanks - yes the garage owner says it is water freezing. We have fitted a new fuel filter during the summer which we drain regularly. There is no way of draining the tank without removing it completely. We have had no problems whatsoever with the engine since last Winter - it's just since the very cold weather again. We are worried about the mis-firing (and the ticking noise!) Don't want to drive the car like this in case we do more harm than good. :hissyfit:

Our local Halfords sell more fuel additives than you can shake a stick at, I wonder if something suitable is available a la France? Given the Gallic prediliction for oil-burners it must be something that has been addressed before. Try this from the US: Bon Chance! Jack

Thanks Jack - I have definitely seen Wynns on the supermarket shelves here. Is that the sort of thing we might need?

Yep ,,, Wynns is good stuff

Cloud point 

Apparently, the "cloud point" is the temperature at which the diesel starts to wax and may create fuel starvation problems. It is variable depending on the particular diesel. I drive to the Alps every winter in a V70 Tdi and park for one week at 5000 feet. The temperature might drop to -10C or so but I've never had a starting problem when leaving and that's on French diesel typically purchased in Northern France. Regards.