Head Gasket....or something less expensive.... I hope

Hi Everyone

I have a 1996 300tdi defender which I've owned for 4 years without issue. My radiator recently dumped all the coolant on the motorway (it was spurting out into the fan on inspection) . Radiator was replaced, not before time, but now I have refilled via thermostat and radiator plugs and bled the system I have constant high pressure in the expansion tank. Starting fyom cold there is immediate high pressure, forcing air out of the expansion tank, soon followed by coolant spraying out. I've replaced expansion cap. No change. I think water in expansion tank may smell of exhaust fumes. no oil in water, or water in oil. Any thoughts????
Thanks

Headgasket..

head gasket ,if it hasnt had one previous it would soon need one in any case as they dont last forever but overheating would have done it, a fairly simple job on a tdi

thanks for your responses

Looks like I'll be busy with my first head gasket then....

This is the exact same symptoms as I’ve just held on my 300 tdi , although mine split the coolant tank head gasket for sure I’d also say