Tricky coolant question, 1982 300D

[300DPETE]

1982 300D

A couple of weeks ago, I started a citric acid flush for my coolant system. When I was near the last flush of clean water to clear out the citric acid (last Friday), the car went out of commission.

So, it's been sittin with plain water since. Today, I drained it (both engine plug and radiator plug), and filled it up with 55/45 coolant before I had it towed to a machine shop.

Now, my question is, if the car didn't get a chance to circulate the 55/45 mix of coolant (by running the engine), is it possible that some parts of the coolant system will still have plain water in them, and will therefore freeze in the over the next 4 nights until I get the car towed back here? I'm concerned that any frozen water might cause a crack in the engine.

Am I worrying beyond all reason here?

Thanks,

Pete.