When installing the service port adapters, do I have to remove the valve core from the original service port?
Usually not. On very few older GM models this is necessary and this is for the high side adapter only. If your original R-12 valve cores are leaking they should be replaced after you remove all the R-12 and before you actually pull the vacuum. You can test for leakage by placing some ester oil on top of the valve core and seeing if any bubbles occur. All ID low side port adapters fit over the existing R-12 ports and do not require the removal of the existing schrader valve core. Most cars have high side ports that accept the ID high side port adapter that fits over the port so again, in this case, the valve core does not have to be removed.
