So, I came up with one way of testing heater cores, but I think that it only works when they are atrocious. The two not in my car both passed.
There was the other way that I thought would 100% work, but either I have three bad heater cores or there is a flaw in my testing. I asked in a bunch of places and that did not go any better than... ever.
In no particular order I received: Trolling, obvious advice, and useless advice.
Did any of you play Streetfighter Two? That was popular when I was in seventh grade and when we first started playing we were trying to figure out the moves. A friend and I were discussing Zangief's screwdriver, also called "Spinning piledriver," "Screw piledriver, etc." You know, this move:
When was Santa Clause in Street Fighter?!
A classmate said "You just go into the secret thingie and get it!"
Clearly he did not have any idea what he was saying and that is often my impression when people tell me what to do.
I honestly do not know what to do. Do I go ahead and install #3 being fully prepared for there to be a #4 and potentially a #5? There must be someone able to help me, do I write a letter to Santa?!
Someone suggested connecting the heater core through the engine bay. I looked into a few things and found this picture:
Clips?! The heater core is supposed to have clips?!
Me to heating system: With this clip I thee wed:
This Miata had them! Where do I find clamps for my Civic?!
