coolant problem

Hi guys, quick question I've moved from restoring my MGF to a ZR some of you may have seen it before martin used to own it known as ziggy.



Anyway that aside I have rescued another 160 ZR that had HGF I've fixed and replaced the head, from what I can work out the rad split down the side the plastic part and it was stainless and rather new.



I am assuming that as it dropped the water and overheated hence the HGF it had a single shim gasket so prob not the best to start. It all sorted now and drives well, but I've been struggling with the coolant.



It appears to be under too much presure, the hose from the top of the rad blows up like a balloon and unless I undo the expansion tank cap and release pressure and water I fear it would burst!



So I undid the bleed screw and there's no air and a nice stream of water/coolant have I missed something?



Fluid pumps into the tank so I assume the pump is working fine?



I drove the car round the block and the temp guage rises over the half way so didn't push it any further, theres no hot air either blowing into the car?



Any ideas

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