1.9 dg wbx overheating / cooling issue

[filiphiruta]

Hi guys, so i recently started to work on my newly bought 1983 1.9 dg wbx camper and i have some problems i cant solve with the cooling system, i tried almost everything, i replaced the parts i tought were the problem, and still does not work.
Parts i replaced :

Thermostat

Water pump

Coolant bypass steel pipes

So the problem is basically that coolant does not get to my radiator and it starts to over heat.

This is what i did yesterday as it was the first start after i replaced the parts, as the system was partially drained i wanted to cleanse it with distilled water so i can go from g11 to g12 coolant. I got the expansion tank full of distilled water ( cap open ), radiator air bleed screw open, i started the engine ( it does not have the best idle ), i let it run for around 15 minuted or so, i checked to see if the thermosat opens and coolants starts to go to the radiator, it does open but unfortunately it didnt reach the radiator somehow and the water started to boil and splash out of the expansion tank everywhere, i stopped the engine. Did i do something wrong? I would love some help, the warm coolant BARELY got outside the engine bay on the coolant hose that goes to the radiator, also heater valve was open, same as the radiator, no warm coolant got to the heater core.
Please help me because im starting to get out of ideas and options and i might tear all the coolant system out and have a look at it or so

As always thank you for taking the time to read my pathetic questions

[Aidan]

usually if coolant boils it can be simply because the dalek cap has failed and isn't holding the coolant under pressure so it acts like water and boils at 100', so put your spare cap (you must have one - essential spare, like water pump belt) on the expansion tank and see if that helps
check also that no water is coming out of the failure hole on the water pump which can happen when water pump fails (impeller parts company with shaft, seal fails)
water should circulate around heater circuit if the temp slider is open, only really circulates around the cooling system once the thermostat opens, before then it is in closed loop state bringing the engine swiftly to working temp
it could be rad is blocked -- but you would have figured that out when changing front to back pipes as you would have flushed the rad while the pipes were off to remove any crud
double check with diagrams (in Bentley, see general discussion post) you have coolant pipes front to back connected correctly