Does my Peugeot 407 have a head gasket problem?

For at least six months I have had a coolant leak, but there are no signs of a leak anywhere. I am now putting in one litre as frequently as every two days, after mileage as low as six. On the other hand, if I fill up with water before a journey I can do 50 miles without any drop in performance or sign of overheating, although I would have to put another litre in for the return journey. The oil dipstick is clear but the oil filler cap is coated with mayonnaise-colour gunge which I am told could indicate a head gasket problem. The car is a 1993 Peugeot 407STI with 103,000 miles.

Asked on 16 September 2010 by Lotsa

Answered by Honest John
Yes, the mayonnaise could indicate a head gasket problem. But also an airlock in the cooling system could be blowing coolant out of the pressure cap. Have a look for any sign of that before worrying that it is the head gasket. There's a FAQ telling you how to get rid of an airlock at HJUK.
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