Hello-
Hopefully there hasn't been any permanent damage to the car. With luck he shut it off before anything bad happened.

Heater control valves on the 7/900 cars are a known failure point, and should be replaced any time the car has had a history of overheating. They're just plain fragile, and it's possible that one was cracked or broke from the heater hose servicing.

Not too expensive a part, so plan on replacing it anyway.

It's also possible the coolant was overfilled. These cars don't have any place for the coolant to escape to if it's overpressurized or overfilled. The whole system is under pressure. If a car is over filled and then driven, it can blow out the coolant cap on the reservoir. I've done it once or twice.

Good luck with it!
--
::: Rob Bareiss, New London CT ::: 92 244 M47 212K ::: 90 745GL M47 275K ::: 90 745T AW71 213K ::: 90 745T Parts Car ::: 88 245DL SOLD! ::: 84 242DL Project ::: 70 VW Bus ::: 70 VW Pickup Project ::: 71 VW Notchback :::