Basically my header tank (alloy spec r ) gets absolutly ROASTING HOT can hardly touch and get a fair bit of pressure if tryin to open cap but is not that bad if let my fans go off, and if i have been giving it some i.e 120ish+ it seems to be spraying water from somewhere ? is defo coming from header tank i.e cap fans come on as usual and go off , and car drives and runs great but this water temp thing is puzzling and annoying the tits off me temp sits between O and R on guage when driving round it is stage 3 with pace rs500 cooler , so any ideas guys on this

any help appreciated

 

Don't trust the std temp gauge, they are far from accurate.

Prob a good idea to get a new cap, the rubber seal may have worn on yours.

I would also expect the header tank to be really hot after a spirited drive, it contains very hot water and will be hot to the touch. Try touching one of the water hoses, they will be hot too

 

Would any of this effect the pressue and the fact it sprays water when giving it some

 

you should first check the real temp on the cooling system.

but expansion tanks cap is important piece on cooling system. i would renew it, because its cheap part, and if its old, it could leak or it could not let pressure out.

 

check headgasket, mine was blowing between cylinder and water, although mine was quite bad under load on boost when going down the motorway it would spray water through the gap between the bonnet and wing. Good luck

 

You can get a high presure cap from spec r that will just replace your current one and cure your problem