While checking all my fluids i noticed a VERY minute amount of white foam under the relief valve on my coolant cap. About a year ago I had the head gasket replaced and the only known issue I have is a suspected small leak on my water pump which will be getting fixed soon. I check the coolant every other day for piece of mind and haven't noticed this before. Anyone have any ideas as to what may be going on? There has been no noticeable drop in coolant btw...
98 disco
as it sits in my driveway it has exactly 122,000 miles on it.
.Thanks in advance

 

If you only do short 3 or 5 miles drives, the can not warm up enough to burn off any condinsation and this can happen. It off course happens when a head gasket fails but usually there is a lot of custard in the cap at that point.