S320 CDI Over-heating?
 

Hi all, this is my first post, I was driving home a few hours ago when the car decided it wouldn't allow me to go over 20MPH, and the lights on the speed-o-meter would only illuminate upto the 20MPH sign shown...

Turned the car off, it was okay for a while and then it wouldn't go over 20MPH again.

Left it for a while again and managed to drive home (about 5 miles at 40MPH) when the temperature gauge, which usually sits at 80 degrees rose upto about 100, so I think the engine is over heating?

No fault codes have come up, but when I arrived home and lifted up the bonnet it was really hot.

I've checked the water and coolant levels and they are fine, so i'm abit lost as to what it could be?

Its a 2002 S320 CDI with 70,000 miles on the clock. I live in the UK so I don't know if the car model is any different from the cars in the states apart from the right hand drive but I hope not lol!

Any help very much appreciated :)