1994 Buick Century-strange problem

I have recently had problems with a 1994 Buick Century, 6 cyl, with approx 100K miles. It seems like these problems could be symptoms created by another problem, but I'm just guessing. Any advice would be greatly
apprecaited.
Slight loss of coolant with driving, does not overheat, does not loose enough to run low. I just keep topping it up. It might loose between a pint and a quart after several hundred miles. I can't find any signs of external leakage. I have a professional quality cooling system pressure tester; using it I have not been able to detect any signs of leakage. System holds pressure cold and hot. Running the car with the pressure tester the guage holds steady, does not fluctuate. The radiator cap tests out ok. This problem is still occurring.
About 3000-5000 miles after the above started the porcelain on the #6 spark plug cracked and was causing shorting to engine head and misfiring. Replaced all plugs and car ran fine.
5000 miles after the cracked plug the car started missing. It was #6 cylinder again. The plug wire had developed a problem. The plug wires have only been on the car for about 15K miles. After removing from the plug wire the metal end that attaches to the spark plug, none of the carbon strand was visible. I had to chop off about an inch of the wire to find the strand. There was a lot of black dust on the metal end off of the plug wire. It looked like the carbon filament had been destroyed and turned into powder as far as an inch back up the length of the plug wire. After chopping off an inch of the wire, stripping a small length of the insulation, reattaching the metal end, and reinstalling the boot, the car ran fine.
The only idea that I have as to a possible common cause would be the cooling system. Could it be that there is a blockage in the water passages in the head and that the spark plug for #6 is not able to dissipate its heat effectively?
Any other ideas, good guesses...anything? I have never encountered anything like this before.
Thanks,
CW Montgomery, AL
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GM made more than one v6. Which one is in your car?
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The engine is the 3.1 with sequential fuel injection
" Paul " <"=?x-user-defined?Q??= Paul

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Craig W wrote:

Sure sounds like the typical intake problem with the 3.1. If you don't know about it you should read up on it. There are tens of thousands of hits on Google about it.
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Thanks a lot. I'll check that out.
CW
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Craig W wrote:

and turn the engine over a couple of times to see if there is any coolant in there.( after car sets overnight) ernie

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