V6 Mondeo squirting out of radiator header tank

[supersport]

My 97 V6 Mondeo has started venting the odd bit of coolant out of the top/around the header tank filler cap.

Also there is some faom type gunk in the opening. It is not oil as there is no mayo in the oil and it isn't oily in the water.

The car isn't over heating, when it does get hot say stuck in traffic the radiator fans come on then then it cools down as expected.

The car has done 153K.

Any ideas what could be causing it.

[nelly1]

Sounds like a head gasket is on it's way out - Cylinder--->Coolant Gallery.
This is pressurising the coolant and the cap is venting the excess.

OR the cap is knackered - this is by far the cheapest thing to try.
If this makes no difference - a compression test is on the cards.

[Kitchski]

Check to see if your car ever had the upgraded water pump fitted (basically any non-gen one) as the Ford ones used plastic impellers which can warp/melt causing inefficient cooling, which in turn boils one of the H/G's, ususally the front I believe.
The aftermarket ones are metal, so no problems with those, but the window you get once the pump has failed is very short I'm told. They're quite easy to replace luckily too, they run off a seperate drive belt on the gearbox end of the front head.

If Ford used metal instead of cost cutting plastic, their cars might last longer! Check out the newer Zetec-S lumps...they have plastic cam pulleys!