|
I don't think in most cases they are bad but some manufactures struggle with sealing the plastic parts to metal surfaces. Honda hasn't been able to design a plastic valve cover that doesn't leak oil on their turbo 4 cylinder engines. VAG hasn't been able to make a plastic water pump or thermostat housing that doesn't leak coolant for a good decade. I think they work better on parts like intakes as with 3D printing they can now make intakes that are lighter and flow much better than cast aluminum. In general most engine bays today are filled with plastic and cars today are as reliable as they have ever been so I don't think it's much to get concerned about.
|