The upper and lower kingpin bushing bolts appear to be frozen in place on my 1959 ponton. Much squeaking. The nipples will not accept grease from a handgun, so I decided to try to turn, first, the lower bolt. First, lots of penetrant for a couple of days. Then, I put all the muscle onto it I could, but no budge. Two things I did not do was to apply heat or to use a pipe extension to gain more leverage on the wrench.

I didn't use a pipe extension because of fear that I might snap off the head of the bolt, leaving the shaft in place and really screwing myself. How hardened are these bolts? Is my fear of snapping off the bolt head real or not? Some advice I have received suggests that these bolts are so hardened that they will eventually turn with enough leverage because the bushings are inherently softer.

Any thoughts and advice based on experience? I am also considering finding an air-driven grease gun at a shop to try to force grease in. One fear I have is that the pressure would blast out the nipple and strip the female threads, again screwing myself. Thoughts? Suggestions? Experience?

Thanks much.

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Douglas
1959 M-B 220S cabriolet