Explain these lines -

‘She makes too much steam—you want to hang the monkey wrench on the safety valve!’

The author had brought a watch and it had worked flawlessly for eighteen months, before he let the watch run down. He got the watch repaired seven times from seven different people in hopes of restoring the watch to its original condition. The last person to whom the watch was taken, had been a steam-engineer in the past. He was an old acquaintance of the author's and he wasn't a very good engineer in his days. When he saw how hopeless it was to repair the watch, he told the author 'she makes too much steam' and that he wants to 'hang the monkey wrench on the safety valve'.