kingpin bushing problems
I have removed the nut on the lower kingpin bushing bolt and put all my muscle, including with a breaker bar, to get tthat bolt to turn. It won't budge. The bolt seems to be frozen in the bushing. (The nipple won't accept grease easily.) I had a bottle jack under the control arm to relieve force. I did not apply heat and I did not use an extension pipe on the breaker bar. The reason for no extension pipe is that my imagination envisaged snapping off the bolt head, leaving the bolt shaft stuck in place inside the bushing and really screwing myself.
Before trying the breaker bar, I soaked the whole area, including the zerk hole after degreasing it, with penetrant for a couple of days. I also vibrated a hammer drill on the bolt ends to attempt differential vibrations to try to break up internal rusting.
For those experienced in kingpin suspensions, is that fear warranted? How hardened are these bolts? If breaking the head on these bolts is a legitimate concern/fear, what are the suggestions for getting the bolt to turn for partial or complete removal?
1959 M-B 220S cabriolet