White steam from the exhaust, misfire & petrol smell in header tank?
 

Not a scoob but technical related ;)

My sisters Primera gt started to misfire and overheat yesterday and had no water in it.

I had a look at it earlier and it was switching between 3 and 4 cylinders and smoking (well I thought it was smoke :o) When I looked at it this evening I noticed that plug number 4 was wet but I thought it was flooding up because of the dizzy cap being worn but the steam out of the exhaust smells like coolant :eek: Just to reasure myself I took the lid off of the header tank and that had an incredibly strong smell if fuel :( That's the head gasket gone isn't it? God knows why it went, maybe it got a hole in the rad then ran out of water and overheated or it did the water through the bores but I don't know.

When the car runs it's only on 3 now and the smoke/steam from the exhaust is so bad the car's not driveable :(

Everything you mentioned points towards the head gasket being blown, pull the dipstick out and check for milky deposits as this is a good way of being totally sure, if there is no milky deposits it *may* not be the head gasket and...... it all depends if the gasket has blown between the oil feed ports and the coolant ports and or the cylinders :)

AP

Thought so. I didn't check the dipstick but the filler cap had a milky grey oil on it but it wasn't like mayo like you'd expect.