past perfect/past perfect continuous
The mechanic had been taking/had taken the engine apart several times before they were able to locate the source of the mystery rattle.

Could you write which is the correct option in your opinion?

Question

past perfect/past perfect continuous
The mechanic had been taking/had taken the engine apart several times before they were able to locate the source of the mystery rattle.

Could you write which is the correct option in your opinion?

Answer

Had taken is the correct answer.  You would only use 'had been taking' if the mechanic was interrupted at a specific point in time, and then you would start the second sentence with 'when....'

Answer

The correct form is: "The mechanic had taken the engine apart several times before they were able to locate the source of the mystery rattle."

Answer

Had taken