Stanley Rayburn Superstar Overheating

[sion1060]

Hi all. I have a Stanley Superstar oil burner. It's been absolutely amazing for years but last year I had this new all in one Mcdonald tank fitted, which is great also. But the problem is if the dial on the rayburn is on 70 degrees and heated up the tank.. As soon as the water pump turns off it starts to over heat, plus sometimes makes these big banging noises. It doesn't go off if it's on 60 degrees but the problem is it's not quite hot enough to do the heating and hot water the same time.. Seems 70 degrees is the magic number. How will I be able to bypass this to somehow keep the pumps running for like 15 minutes after the rayburn has turned off. Or something to add to cool it? Any suggestions? Thank you very much