[Warning Light] problems

[opahno6]

Hi. Can anybody help me with a problem with my berlingo van? I recently bought a 16 hdi with a broken engine and fitted a 1900 engine, running gear and all the electrics etc. It ran like a dream for about 3 weeks till the temperature gauge sat in the red as soon as i turned the key, the warning light flashes and the injectors clack like a tractor. I've replaced the thermostat green sensor and checked every earth that i can find on the van with no luck. I'm hoping that with so many berlingo's on the road that somebody can help, it would be greatly appreciated. Thanks.