There are severe differences in the grades of plastics. If you ever have the opportunity to work on something like a LS430, then you'll see what good plastics can do. Half the radiator is plastic on those and I've never seen one leak. I've seen them in accidents and still hold pressure. Then you look a a modern ford and see them leaking from the seams when they're brand new and need a warranty replacement. Getting 20 years of use out of an all brass radiator without any repairs is pretty special. Getting 20 years of use out of a LS430 radiator is normal.
I ordered a radiator for a 1996 4runner for a friend a few years back. It arrived via UPS and when I opened the box, the plastic overflow hose nipple near the radiator cap on the upper plastic was busted off. It wasn't in the box. I contacted the vendor, they shipped another out that day and sent me a return ups label for the first. When the second arrived, the same nipple was busted off but not in the box. They sent me another return shipping label and my friend ended up buying a new radiator locally. I think someone in the parts department was sending out factory rejects.
So, other than that weird experience, I agree, radiators are better these days, they are an exception and generally much cheaper to replace than the copper versions of yesteryear.
Lived it. New rads can take a beating. That's why you don't see a lot of radiator shops anymore
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