So i when i picked up my 84' GSL-SE the heater core was leaking (and no it was not the control valve) so i picked one up from my local parts store. Spent a day taking out the dash and replacing the core.......fixed right? wrong still leaking misting my windows i was so pissed off that i walked away from the car for a week. So onto checking to make sure all the rubber hoses were not the problem i could find no leak. So today i went down to my dads house he has a shop so i didnt have to do this in the rain. Removing the dash with 2 people is so much easier, got the dash out took the heater core box out and took it apart and sure enough the damn core that was brand new had a crack in one of the tanks! WTF...so back to the parts store to get a new one! well im glad to say its back together and leak free! anyways guys never asume a new part that has been inspected is acually good

 

Someone had the same issue with starters from NAPA. I think he went through 3 starters that were wired wrong until he finally got a 4th that was wired correctly that would go in his car without instantly cranking the engine haha I agree, never trust a part until it has proven itself to work. Welcome to the forum and awesome post!