Ka. Ka. Ka. Sound from the engine

Hi
My Mitsubishi Pajero Shogun Exceed V75W Yr 2003 began to produce a ka. Ka. Ka. Ka. Ka. Sound from the right side of the engine, I had just done 23 km that day.(Total mileage is 173540 km).
-then the heating gauge went up and suddenly the car shut itself off and I parked by the road
-water vapour fissed out from the breather, coolant jug was boiling, and on opening radiator, a geyser shot up
-the engine wouldn't start with the high temperastures
-i let it cool off for 4 minutes-the gauge came to halfway point and I added cold water into the bubbling radiator.
-after 10 minutes the ignition started the engine but the ka. Ka. Ka. Ka. Ka. Ka. Sound was way too loud, always coming from the right side of the engine. And on engaging drive, it shut off.
-after 1 hour of towing the car home, I restarted the engine, engaged the drive and reversed and parked the car. The ka. Ka. Ka. Ka. Ka sound is still there, and madenning.
-There appears to be no leakage of water
whats the problem, how seriuous is it and how do I solve it.
regards