My 1200 GX sedan runs hot, and i have no idea how or what the problem is, new 13psi radiator cap, new radiator and a new waterpump and also a 72degrees C thermostat. When the car is almost boiling and i wouls stop, the hoses are hard as a result of pressure in them.Pleassssssee Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This is a normal problem on almost all datsuns.
What radiator did you fit?
Did you just let it be cleaned out?
I will not reccomend it. I cleaned mine out and it still overheated. I later discovered that it STILL was dirty in some of the places. I recored mine with a tripple core that has more of those fins between the vertical pipes that creates the radiator.
Mine now does'nt overheat anymore. Even at 140km/h on the freeway on hot days it stays 1mm just below the middle line of the guage.
Did you check your waterpump?

I switched my radiator with my dads, and his 1973 1200 ute ran as cold as ice, with the heat cage bearly lifting, hot or cold, with the one i have in my car now. New waterpump and if you let the car idle with the radiator cap open, you can see the wter swirling???

If you know the radiator is good, your cooling galleries must be stuffed with rust buildup. Have you, and all owners befoe you, run coolant? Or just tap water?

mine has always ran cold as ice and now with a new radiator I think it run a bit to cold.

Like chris said I think the galleries are blocked.

Your thermostat may be bad, stuck partly closed and not allowing the water to flow.

A simple test is to remove it. If then it keeps cool you know that's the problem.

By the way, I recommend getting rid of the 13 lb cap and use a 5 lb cap. The high-pressure cap is solely for 100-degree (212F) thermostats. A lower pressure will help prevent leaks in the radiator, heater core and hose connections.

Check all the elements posible. If you have a cleaned radiator, professionally cleaned, perhaps you commited the same mistake I comitted in my jeep years ago. I took the radiator off the car, and got it pro cleaned. Re installed it. The clylinder head and the engine water passages were full of rusted particles and that re clogged the already cleaned radiator.
Take the radiator off again, and run water through the engine water passages w/o the radiator in place, all the water flowing through and out. That will rid your engine of gunk and crap so that the radiator , which will have to be cleaned up again professionally, does not get re clogged.

Or take it to the shop and have them take the radiator and ask them to pressure clean the block, radiator out or bypassed.
Then after the block and the radiator are cleaned, use new hoses too, because old hoses have pieces falling off and also colect rusted metal that later on cloggs up the system.
I learnt a trick with thermostats. It pays to drill a hole in the upper part of it, a small hole. That is insurance against a sticking unit. If that happens, you will run warm, but not boiling hot.
If you can, safe yourself trouble and get peace of mind, get the block cleaned, re clean thge radiator ( if you take your car for the block pressure flush, I bet the shop will re clean your rad free of charge.
Get a new water pump, and thermostat.
An overheating engine can end up in valve warping and more headaches.

i feel your pain.
I tried all the above and gave 3 radiaitor flushes as well as flushing the system out of the block etc. using a 45 :55 mix of anti freeze anti boil and temp is fine, except at 5000 rpm in 4th where it starts to climb from 190 f to 200f but seems to stabalise there.
At idle runs a whisker over half on the stock gauge but 3/4 when at 200 deg f (93deg celsius i think).

Raditor may have been fine in your dads ute but you may have buildup in your block.

could also be a collapsing hose when driving (cant simulate that at idle needs to be under load)

trial and error. Try a bottle or two of radiator system flush and then flush with water then add coolant. see if it works.

Hey datodude,I'm running coolant and the previous owner did aswell and i cleaned all the ports when I rebuilt the engine. I hope I can find and solve the problem because my gx is suffering and i know that the double valve-springs is softer as a result of the heat, because it can not rev more than 5600rpm.

Have you got a temp gauge that you can test where the hot spots are.