Hi all changed my thermostat, however still got a leak from the pipe at the back, where you put the metal retaining clip. Does anybody know what this pipe is. I'm not sure why it's still leaking its hard to see, might be a crack.

I have provided a picture of where the pipe connects to on the thermostat.

 

The plastic water-pipe, connects thermostat housing (where you indicated in above pic) to water pump. I strongly suggest you replace the water-pipe any time you replace the thermostat housing.

 

don't even say strongly suggest... just say you HAVE TO... I made that mistake when replacing my thermostat housing, within a year it snapped at the o-ring land. They are cheap enough to just get it done at the same time.

 

That attaches to the water pump pipe. We always replace it when we do the thermostat.
https://www.waymotorworks.com/water-...9-r60-r61.html

 

And it is infinitely easier to replace if you just go ahead and remove the intake manifold.