Renault scenic 2 2008 coolant/engine temp overheating.

[Glaza2946]

Renault Scenic 2 1.5dci 7 seater 2008. Just bought.
Having a problem with the dash temperature gauge rising above 6 bars. (Closer inspection of engine bay revealed there's a definite heat issue because you can feel the hest rise and lower) Checked oil and was basically empty.
Topped up oil, coolant ect. Noticed pipe connected to (below window wiper, middle area) head gasket has been loose in past or possibly disconnected due to amount of oil residue around the area (looks like it's just been blowing out to the rear of head casket). Also, it seems like oil at one point has seeped down to bottom area of drivers right arch.
I'm able to control the engine temperature to around 3-4 bars using air con, plus full blower. Which then leads to the second problem...
When a.c. is on, after a few min the car begins to leak clear water at a steady trickle pace, all underneath the vehicle. I had a similar experience with temp in mothers renault. Oil cap burst open on motor way, oil everywhere ect... temp gauge shot up for 3 days but slowly stabalised with clean up and fresh oil.

So basically what I'm trying to say is. There are no warning lights on, it's just past 12month mot, car runs great. I'll be changing pollen/air filter. But what can i do to stabilise the engine temp without resorting to the a.c. + heater. Is the water leak a sign of something? Is the coolant causing the problem? Anything would help guys. Great site, I wouldn't have got to this stage without it! Cheers.