Plastic heater core connectors ????

Since 1981.

All of them.

Yes.

Not true. Few are brass. Most are plastic or aluminum.

It happens. "Common" is a relative term. Everything will fail eventually.

Yes.

connected

I changed my 83 chev core and the old was brass/copper and so was the new from NAPA.

GM might of started using plastic around 1980?

My 89 Cavalier Z 24 heater core split open ( luckily ) while backing up the drivewway one night after returning from the theater at 2 am. Anitfreeze pour out at a rapid rate all over the driveway thanks to the drain tube in the firewall. The plastic heater hose pipe broke right off the side tank. The core was 8 or 9 years old.

My 91 Bonneville heater core is also has plastic tanks & aluminum core. It had a very slow seepage leak that sealed itself up for awhile. Upon replacing the ECM in 2004, I noticed some dried up residue on the bottom of the HC cover under the dash. About two months later, wetness began showing so I replaced the core. It was 13 years old.

Its is probably cheaper to make plastic rather than all brass or all aluminum. Also reduces weight which manufacturers are always trying to shave off cars.

Good Luck

Harryface =D8=BF=D8