Overheating when driving

Hi,
I am having an issue with overheating. It started last night while i was driving a short distance. I waiting until this morning to check the water. I only needed to put half a litre in. While it was idling and coming up to temp it was fine the gauge was sitting just under half as normal. Then i went for a kilometre drive and she climbed to hot reasonably quick. Then when i stopped and left it running it started coming down.

I was thinking a thermostat problem, so i have one but the guy at repco said it could be air pockets, whatever that means. How do i find out for sure???

Please help. Thanks

if your engine has a few K,s clocked up there is a chance that the radiator has a partial core blockage caused by coolant jelling up. try the thermostat first and if still the same repair or replace the radiator. other issues can be the fan hub.

If you've been in the mud lately also check there isn't any stuck in the radiator!

The first thing I would check for is a kinked hose which will restrict flow and cause overheating.
Then remove the radiator and give it a real good flush, several times.

I removed the housing on the left side of the engine, the one attached to the top hose. But there is no thermostat in there. Where is the thermostat kept???

It's on the other hose, in the housing under the alternator. Two bolts have to be undone from the front of the engine and one from the side.

If you have a fluid coupling on the fan, check that. Easy to do: when cold, it should spin fairly freely. Get the engine to normal temp (or slightly overtemp, doesn't matter) and turn the engine off. Spin the fan - it should be quite stiff and hard to turn. Do NOT put newspaper in a spinning fan - you don't want cracked blades! If the fan isn't difficult to turn, there's your problem - when the engine is working hard, it's unable to turn the fan fast enough to draw enough air through the radiator to cool the coolant.

Other than that, check as above.