Cannot turn nut on top of strut. Would cracks in the spring seat be affected by cold temps. ?

XC70 2004 Have a clunk in the front when going over bumps. Had the tie rod ends and front end aligned by Volvo dealer. (53K) Reduced the clunk but did not eliminate. Replaced the sway bar links myself but still did not eliminate the clunk. Clunk seems to be greater in cold temps (20 F). Can feel the...