We had two Volvos when our kids were little, a sedan and a station wagon. We took the station wagon to San Francisco about 1995 and when we got back to the car it had dumped all its coolant on the parking garage floor. The tee valve that shunted coolant to the heater core was plastic. One of the arms of the tee broke completely off.
Putting a plastic valve in the coolant li e was the stupidest design decision I ever saw. Nothing but problems with those cars, big and small.
We bought that car about 34 years ago.
I didn’t mention this in the first post I talked about this in, but European carmakers were at the forefront of replacing underhood metal parts aith plastic ones. BMW and Range Rover being some of the most notorious makers.