Back in 1995 one of my company car drivers went through a ford (of the water variety) in his Cavalier 1.7 td - the car spluttered, had a cough and from that day on always had an uneven idle and smoked a fair bit at tickover. It did a further 40 odd thousand miles before the headgasket went. when the head was removed one piston was noticably lower in the bore than the others. Further investigation revealed a bent rod from ingesting water.

I was amazed that it went for as long as it did with a bent rod, also how it never locked up is beyond me??