Running Temp Issue

[iruvyouskyrine]

Well, yes at idle. But also driving it doesn't get below 84, so that it's acting as an 84deg thermostat realistically.

[89CAL]

It's already been said, but is their sufficent flow through your raditor? If it is at idle and cruise speed then check radiator for blockages etc. Also check that nothing else is mounted in front of the radiator that is producing hot air flow (e.g an oil cooler with 100 degree oil running through it is going to heat the air before it hits the radiator)

When you say driving, is that just street driving or hard driving?

[KiwiRS4T]

Yes I know that kiwi, I think you need to re read my original post. No matter what temp thermostat I put in it, it still idles at 84deg. The current thermostat I have (65deg) should be regulating the idle temp to 65ish degrees but it's still sitting at 84.

And yes I have properly bled the system.

OK I have re-read your original post and it seems you do not understand that once a thermostat has opened then it has no ability to regulate the temperature (unless you are operating in freezing conditions when it might close again). That is why regardless of the opening temp of your thermostat ( and you say you have tested them and they open as advertised) your operating temperature remains at 84 deg. Talk of "headroom' is a blind alley. It only takes a few minutes of hard use to raise temps quickly and cooling is only available by the radiator and oil cooler. Problems can be caused by blocking of the radiator by oil cooler and intercooler placement, or some fan arrays and can be ameliorated by air ducting and turbo or exhaust wrapping.

[KiwiRS4T]

You can easily test the operation of your thermostat in situ. Turn the car on from cold and feel the waterhose. Let it idle and you will be able to tell when the thermostat opens as the hose will suddenly become warmer. Check your water temperature gauge. After it has warmed up the radiator if your temperature continues to rise you can rule out the thermostat as the cause since once its open it can do no more to reduce the heat.