Van stalling and not running correctly

[InterGAS]

Once of our vans is not running well at all.
After the van is started and driving for around 10mins the temp races up to high and causes the van to stall.
The water level is fine and I have checked the oil cap and tank and there is no white just pure black.
If I remove the water cap the van runs fine, does not over heat and as you can expect I need to keep putting lots of water as it spills over but this is the only
way I can drive at the moment.
Any ideas? I have been told cyc head gasket which I just cant see it being that, some have said water pump, stat and even the water cap itself.

Any ideas?

2001 260 swb transit, righ hand drive, UK spec.

[winterheating]

do blowers get hot
if its cutting out will be cos temp is in red, will go into limp mode then cut out.
it wont be stats as its over heating after only 1o mins, if it were the stats the blowers would be red hot first unless water pump wasn't working

[InterGAS]

heater blows hot air for maybe 40 seconds then gets cooler and cooler and cooler untill freezing.

[winterheating]

that sounds like no water circulation at all, the engine temp boils up wich gives a breif circualtion of hot water through heater matrix, you need a new water pump.

[InterGAS]

Not sure if this helps also, when I squeeze the pipes the tank bubbles, although the righ hand side is always hot on the pipes but bottom left is cold, this points to water pump also?