Ok I have a 00 Si. The past few weeks have been crazy. The temp hand started rising and lowering on me a few weeks ago so I tried to solve the problem starting with the cheapest first.

So after 3 thermostats, temp sensor, therma fan swith, relay, flushing the radiator, water pump and changing all belts, even tried a different cluster and it still isn't fixed.

The temp hand keeps going up and down and have no idea what else it could be. The head gasket is good I have checked all symptoms for that.It isn't smoking, steaming, boiling or bubbling or any of that and it will eventually fall after it gets to the H on the temp gauge but have no idea what else to do. If anyone has any Ideas on what could be causing this I would appreciate the help. Thanks