Thanks, Belinda, for this copious information. I appreciate it, but I'm quite sure that neither rust nor solidified, old grease is the problem here. The fittings are clean, without a trace of rust and the balls and springs move freely - I pulled a couple and checked.

I had the control arms apart for inspection and seal replacement when I got the car seven years ago. At that time I replaced the grease fittings as well. I usually put about 1.5K miles on the car per year and grease it once a year before putting it away for winter. The problem has been with me since grease job #1. I suspect that the obstruction is mechanical, but considering the parts that are in there, I just can't visualize what it could be. I'm not at all enthusiastic about tearing the whole thing apart and then finding that there is nothing wrong inside either. Especially because that means I'd have to get another front end alignment done, and the people who know how to do that properly have pretty much kicked the bucket. So, I was hoping that someone here who had had the same problem could tell me her/his fix. But I'll try the heat gun approach.

relube these fittings every 750 miles
That gave me hope for a moment because I thought that such a short lube interval might mean that they actually expected very little grease to go in there - hence, grease often with only barely noticeable amounts at a time. No dice, however: my PV544 manual says every 1500 miles, just like all the other front-end lube points.

Bob S.
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'62 PV544 (B20, M41), '71 142E, '93 240 Classic Wagon.