Wierd Noise and Temp Gauge Jumping

Hi all, my temp gauge has been jumping aroudn now for about a week, when doing 0-80 aroun town. When on the freeway doing a constant speed it sits where it should, but just yesterday at certain speeds theres a weird noise coming from under the bonnet at certain speeds/RPM, like a whirring sort of sound. Any ideas ?

PS the radiator is full, and thee is coolant in the reserve tank.

Thermo fan not getting caught on shrouding? Could explain clunking and heat issues

Whirring sound could be the power steering pump being low on fluid but that shouldnt affect the temp. Could be the viscous fan hub, there's a post somewhere on how to check it.

Checked the fan, nothing rubbing, all fluids are full. Will search the forums for the fan hub issue.

Checking the fan hub is easy.

With a cold engine: wobble it. Make sure it doesn't wobble on the shaft.

Now start the car and get it to normal operating temperature. Pull over, turn off the engine, pop the bonnet. Try to spin the fan - it should NOT move easily. If it does, the hub needs replacing.

The fan moves quite easily, same as when the engine is cold as it does when hot. Maybe its new water pump time? Thouhgh im sure its only 10000km old.......

It's the fan hub. when the engine gets hot, the fan hub is supposed to grab the shaft harder so that the engine can really give it a decent push. If yours is loose when the engine is hot, it's not grabbing the shaft which means it's not pulling the air through the radiator = overheating. Replacing the hub would seem to be the go. Run it past a radiator specialist and ask them for their opinion if you're unsure.

So i wont need a full water pump just the hub ?

They're two completely different components. The water pump might drive the fan, but the hub has to engage the shaft so that the fan can be forcibly rotated to really haul the air through. If the hub doesn't engage fully, the fan isn't driven hard enough. That's a hub thing and it affects the air flow rate.

If you suspect your water pump, the water flow rate will be down and if you can see in the top of the radiator you'll notice it.

That's why it's best to see a radiator specialist near you. My call would be to replace the fan and/or hub because you KNOW that's not 100% and see if the situation improves. If not, then it's possibly the water pump or dirty cores in the radiator (had that issue arise more than once).

Yeah the radiator and pump are both only 10,000km old, no leaking anywhere, coolant still green as grass in the radiator, will take to mechanic let them sort it, but that wouldnt explain the temp gauge jumping and shaking like a bitch would it?

No, that would better be explained by a loose electrical connection.

Fixed teh gauge problem was loose wiring, after doing that simple test by earthing to the block, thanks for that ! Now its just the whirring sound, possibly power steering pump or other bearing not sure, will get it checked, it only does it certain rpm.

Fixed?