I have a signum 2.0t 2003 recently oil cooler failed and discharged oil into cooling system,had a very good 2nd hand oil cooler installed & system flushed 3 times.

all works fine until temp gauge gets to 90c water starts to bubble and blows out of overflow oil cap clean no cream on it

any help appreciated 

There could be a slight possibility that the head gasket could have failed as if there was high pressure in the coolant, that could have led to failure of the oil cooler...just a possibility but worth running a coolant block test (chemical changes colour if combustion gases present).

Alternatively, a more simple and cheap option may be that the coolant pressure cap has failed and not maintaining pressure in the system.