Radiator leak, advise please

The coolant in my rad keeps coming out of the cap when I use my 109.
I've tried replacing the cap but this has not solved the problem.
Any help or advise would be greatly appreciated.
I plan to change the thermostate as maybe this is sticking or blocked

did you flush the rad out and is your waterpump working?

Rad replaced about six months ago, how do i check the water pump is working correctly?

just see how much they are and change it might seem pointless but atleast you know its working or to frighten you , has the head gasket gone ! . squeeze the top hose as tight as you can then rev the engine if the pump is working you should should be able to feel the pipe pressuring no garauntees mind

Get that thermostat out, put it in a saucepan, add some water and bring to the boil. Check to make sure it opens up before the water boils. Water should not be coming out from the cap area even if it the engine is overheating. The water and steam should be going into the expansion tank and then coming out of the overflow pipe. This pipework may be blocked.

Checked there is pressure in the pipe today, seems fine.
Attempted to remove the thermostat but couldn't free it from the housing so it will have to wait for the weekend when I will check the pipework also.

Thermostat out and replaced, cleared the pipes by blowing through with an air line, the leak was coming from the pipe to the expan bottle when it expanded with the heat, seems ok now so on to the next job.........