Ask an expert

hi,just taken a toyota allex 05 ,59000 on clock,drove and felt ok but looked at inside of radiator cap and there was a thin white ,slightly oily substance around inside of cap,it had fresh coolant in radiator .what might this white substance be . thanks

If there are traces of oil in the cooling system, this could be the start of headgasket problems. Are there also signs of a white foamy substance under the oil filler cap?
If theres any doubt, it would pay to have a Pre-purchase inspection carried out, where cooling system testing is carried out.