7745 losing coolant out of rad overflow tube

Hello Everyone,
On-going problem since replacing the water pump on the tractor. When it's running (even for a short period) it starts to leak coolant out of the overflow hose. I believe we got all the air out after the pump change out and we'll check the simple things like a new rad cap and then a new thermostat (stuck closed perhaps??) It's been running strong otherwise and does not appear to be overheating. Couldn't recall if these rads prefer to run a little lower as we keep topping it right up? Anyways any help or input would greatly appreciated.
Thank you

Id start by putting a new radiator cap on, cooling systems are designed to run under pressure, so the new water pump might be running a fair bit more efficiently then the old one. I had the same problem on my zetor.

new rad cap installed and ended up blowing the bottom rad hose off.
Took the thermostat housing apart and it was dirty with a chunk of rubber lodged in it. New hose and thermostat installed, will try to run it with the rad cap off and look for bubbles, if so, it must be a head gasket. If bubbles are present I was thinking of taking the exhaust manifold off to narrow which cylinder gasket is leaking. I don't have a shop manual and really need one, they seem to be hard to track down on the net. Any advice?
Thanks