Oil in header tank

[Flamer69]

Hi all I have a Cosworth Escort and I seem to be getting a very thin line of oil in the header tank. Theres no mayo just this thin line of oil. I have been told this is normal. Any thoughts?

Many thanks

[GreenV8S]

Struggling to think where the 'normal' source would be - water pump seals, perhaps? Not an effect I've ever noticed, but if it's literally just a trace as you say then I wouldn't worry about it. It may not even be oil, possible just muck / corrosion that has been washed out of the engine.

[Zad]

I think I would be inclined to get a compression test, and get the garage to use their high tech "sniffer" and smell for hydrocarbons in the header tank.