Hi. I have recently had my s type v6 engine rebuilt. Also had a new radiator fitted. In the past month I've had to replace the water pump inlet hose twice! I'm guessing it's a pressurisation problem and have ordered a new expansion tank filled cap but any other suggestions or advice welcome.

 

I'm sure thay done it wile doing the rebuild, but double check the thermostat was replaced as well , although it will not cause pressure issues be sure to also check the the correct (orange oats ) antifreeze was used !