318 radiator swap for m20 HELP

[GT BMW E30]

My vert is running hot so I swapped in a new fan clutch. Then a new thermostat 80 degree. No change in engine running hot so I swapped in a 318 radiator (I like the attached coolant bottle). Also, I changed the radiator fan switch. I used a radiator pressure kit to bleed the system through bleeder on thermostat housing. The car begins to overheat after warmup. I noticed the hoses do not seem to be full of coolant. I have not added the level sensor but I wonder if it blocks the flow of coolant as seen in pic. Any other suggestions to look at what can be the cause? Last thing I could think of is head gasket.

[TobyB]

The 318 rad is smaller than the M20 rad...

but no, the level sensor at the bottom of the tank's optional, not mandatory.

(you've circled the drain port in your pic, btw)

And I would think, but not know for sure, that the M42 should cool it enough at idle.

Have you tried bleeding it the normal way? Add water with the screw open until
it spits water- and repeat, repeat, repeat? You have to get the M42 tank
very full to bleed quickly...

t

[ahlem]

I'd check the auxiliary cooling fan electricals and whether the water pump is working properly. You can jumper the auxiliary fan at the temperature sensor in the radiator and see if it turns on both slow and fast.
If only fast goes, you need a new resistor at the fan. You can hear the relays click.
If you run the heater on high and hot does it cool down?