HELP paid contractor 3k to break my boiler

[Harry Wilson]

so we own a 3 story building, it had an old boiler that worked fine, the Tennant had to manually fill the boiler due to no water feeder.

Then we had issues with the electrical wiring to the boiler, so I brought in a contractor and I paid him 800 for 2 new electrical boxes in the basement, 575 to fix the boiler and a new pipe that had cracked. 900 for an automatic water feeder, transformer and Lowe water cut off. Also I paid them 400 for fixing parts on some steam radiators

The guys finish up and I pay them their money as everything works, a week later I notice that the radiators aren't heating but the main pipes that run up the wall are boiling hot. 

We look at the boiler and its burning hot. We call the contractor and he says he will come out and look tomorrow.

When he comes, the boiler is cracked, he said a build up of black sludge caused too much pressure in the system and that now I need a new boiler. 

This is not my fault as I paid 3k in total for him to fix everything and have it all running and surely the system should have been cleaned and some sort of pressure cut off should of been installed?

He is trying to make me fork out another 2500 to 3k for a new boiler, can I go after him for the money?