Not being rude or arguemental, but you mentioned the car was written off, so how can you stand by the 'no long term harm' belief when surely you never got the chance to prove it either way?
We drove it for months topping up the fluid while trying different things to cure the leak without resorting to replacing the entire aluminium piping around the inside of the engine compartment.
Eventually the wife decided it was time to bite the bullet and pay the £200 to replace the pipe.
It drove beautifully for over a month until one day she rear-ended someone.
Ironically, one of the parts within the engine compartment that survived intact was . . . .
You guessed it