Prev post about 1cm of rad neck broke off automatically.
Here is my fix which seems to be working now.
Obtain a 1 1/4" O.D. rad hose(int diam of the one I got is 3/4").cut off 1 " of hose.
Slide hose inside broken neck until it's caught circumferentially by the inside of neck.Slide slightly out again.Apply Superglue around hose.Slide back in.Should be tight fit.
Wait till next morning.
Apply U-fix-it epoxy radiator repair to inside edge of broken off neck and on hose around there.Appose broken off neck to remainder of neck.Thus the hose supports the inside of neck completely no coolant will force open fractured ,now repaired but narrower(was 1 1/4" now 3/4" but only for a length of 1 ") neck hopefully.
Apply epoxy and fibreglass tape to outside of neck to further reinforce neck.
I also bought an extra plumbing clamp to support the top hose,ie 2 instead of one.
Now I understand that there would be turbulence around the narrowed neck,but for commuter use,I think it should be okay.In 2 months,Canadian winter may keep coolant under thermostat anyway for 6-9 months.However,I obtained a Nissen rad already as I did not know whether my fix will work.

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Tom 2010 C250 4-matic Sport (Canada)