Was doing my routine checks, on oil and water.
And noticed that the water in the expansion tank is light grey in colour!
Now dreading what this could be??
There's no loss of fluid, or gunk in expansion tank.
No over heating either.
I did open the rad cover, no gunk or sludge in there either.
Will try to extract some fluid from there tomorrow, to see if it's grey too.

I was told the car had a new rad earlier this year, and can't remember if there was antifreeze in it on viewing the car. ( but I'm sure it would of, as car was previously owned by a mechanic)

Just don't need any serious probs at this time of year, car is booked in to have cooling system flushed and refilled.

Any ideas and pointers would be great, as it could be something minor, and will put my mind at ease if it is.

Car had cosworth gaskets, and forged pistons added on rebuild in 2010/36k ago.
All this is on a 56 hawkeye, with PPP and a few other mods!

Thanks guys