on my sons GLXi 1.6 98000mls petrol, there is a yellowish gunge in filler cap, car runs fine is not losing coolant or oil, is there maybe a breather hose blocked?

thanks in advance

Is it the consistancy of mayonnaise ? :confused:

If so it may just need a good run, (if it only does short jorneys).

If not it could be the start of a blown head gasket.

Change the oil & filter, clean out the filler cap, & go for a longish drive. check it over when you get back & see if the gunge is back.