can we be clear about one thing though as i can't find any reference on any posts are you losing any water from the header tank
for the headgasket to have blown to be the cause of the smoke then the water from the radiator would have to be getting into the combustion chambers and being burnt. if that is
happening then the water level will
go down. i repeat, if you are not losing water then the water to combustion chamber head-gasket seal is probably OK. there are of course other parts to a head gasket, the oilways can mix with the water, the oilways into the cylinders, the cylinders can leak between each other, but as we are investigating seemingly water
usage we will stick with that.
i still say though what i mentioned before, blue smoke is oil usage, white smoke is water usage, but GREY
smoke is unburnt fuel.
it may simply be natural, but as we can't see the extent of the smoke it's hard to say. is it making a fog in your rear view mirror or more along the lines of someone following you saying they can see it
i know it is sometimes natural to worry that things are bound to go wrong but i really wouldn't worry if
1/ you aren't using any excessive amount of any fluids
2/ the car runs fine, warms up at the right rate (not too quickly)
3/ it doesn't overheat
as for the emulsion looking on the filler cap it can be caused by the long neck of the filler tube, oil vapour sprays in there from the breathers and lines the inside of the filler tube which is being cooled by the cold air around it causing condensation.
it was a very well documented problem on the early austin maestro's and montego's as they had a similar tube up the front of the engine, every oil change the sludge was so thick it was difficult to actually poor the new oil in
we had to clean it all out thoroughly every service only to have to do the same in 6000miles time. they later improved it by lagging the filler tube to stop the condensation.
i would really just take it in to a garage and get them to test the water for combustion gases, an easy and sure test. you could check the plugs for colour but that might not show up the problem for sure and for the time it takes to take them out the test would have been completed.
don't worry, we will get it sorted one way or another