W123, Electrical

I overhauled the turbo using the mercedessource kit.
Had the turbo and compressor balanced.
Need advice on turbo compressor nut torque techniques.
I used the kit recommendation:
Nut touch the compression wheel, turn CW about 90 degrees using supplied 3/8 wrench and stopped when I judged force to be adequate. Balance marks aligned.
Turbo whine is noticeable when cold engine. Much less so when operating engine temp.
I judge to be a nut torque issue.

The 78 300 D that i rescued from the crusher about 30 thousand miles ago ran hot recently. The driver told me it just steamed up...started knocking and died. (she was not paying attention to gauges).

the water pump had gone south...no water left in system.

installed a new pump. it fires up easily. runs..no bad noises. bo big smoke. no water in oil...But it starts to miss when it heats up and the radiator cap is on. pop the cap and relieve the pressure it smoothes out.

Im thinking it has a cracked head or block and the pressure is forcing steam into a cylinder(s). anyone have any ideas on that. makes sense to me...
but i have never dealt with this type problem before.

anyone ever have any luck with block sealers they sell over the counter.