Took the car out at the weekend and noticed that the temperature guage was sitting higher than usual not in the red, but still high enough for me to notice.

Got the car home and opened the bonnet (water not bubbling or anything) and noticed there are a couple of tiny cracks appearing in the header tank, I replaced the header tank six months ago with a brand new one as it was much worse, and replaced the thermostat while I was at it as I was experiencing similar heat problems, with these two changed the temp became stable again and the needle rarely moved above halfway on the temp guage.

I also replaced the water pump 3 months ago, as that let go.

Anyone got any ideas as to why this may be happening as I don't want to have to keep replacing the header tank every six months as I presume there is an underlying problem somewhere which I can't see.

Also the car is standard apart from a stainless exhaust

Cheers

Ben