[Silver Ghia]

The fact that the mechanic said to fill with distilled water indicates that he used coolant concentrate of the correct quantity, then topped up with distilled water. The reservoir normally gets stained by the old coolant so wont clean up unless the mechanic takes it out and cleans the inside of the reservoir by some means (can be difficult). Flushing wont clean it.

Accurate coolant level checks are done when cold, with the car on a level surface. When filling with the new coolant after a flush, some cars are notorious for air pockets remaining, others are not. Some have bleeder screws to enable air pockets to be bled out (eg. VL Commodore I6). The Falcons I have had haven't needed to be bled, but small pockets do normally remain so I check the next day or so and top up until it stabilised.

When the coolant warms up, the coolant level in the reservoir is normally higher because of expansion of the coolant as it heats up. So the mechanic cannot accurately recheck the level until its cooled down again (also that the reservoir pressure cap needs to be depressurized if hot). Sometimes it takes a few heat-cool cycles before the level stabilises.

Thats why a good mechanic makes the owner aware to check the level after the service.

Looking at eb2montys last post where it was mentioned that the service sheet stated the coolant was "drained and refilled", somehow I doubt they actually did a flush, only opened the draincock to drain out the old coolant, then refilled. Thats why I do that job myself so I know its done properly. I would query what they actually did.

Cheers.