Morning,

I have been trying to pin this problem down for bloody ages now and it's really getting on my nerves...

What seemed like overheating at first, after a new water pump, new KOYO Aluminium Rad & Cap and Nismo Thermostat... the problem still remains although not as bad/frequent!!

Two scenarios...

1) The car warms up and my Greddy gauge shows 70 deg, but the heater blowers are cold, after I have been driving for a few mins, the gauge shoots up to like 90 deg and then back down again, then the heaters are hot...?

2) The car has been running for a while and eveything is normal (heaters are warm & temps are 70-90 deg) then all of a sudden the heaters go cold and my temps shoot up to 120 deg (ouch) if i'm driving the temps will go down fairly quickly, but if i'm stationary they will stay there for quite a while, because their is no air going through the rad...???

I'm down to it being either a faulty thermostat (doesn't explain the heaters going cold though) or the Head Gasket... The engine has been rebuilt with a Cometic Head Gasket and ARP Head Bolts.

Please help... Sorry for the long post...!!

Kim.