Amazing how much pressure builds up when the engine gets warm. The heater core is quite easy to replace, just do a search. Someone found a replacement for less than $50. New O rings are required.

Do yourself a favor, cover the area under the heater to catch the antifreeze. It evaporates very slowly and will remain in the foam pad under the carpet for a looooong time. Plus, it is quite sticky and hard to clean up.

A newspaper will absorb a lot. Just use the black/white sections so that the color ink will not bleed on the carpet.
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My name is Klaus and I am a V♂lv♂holic