temp gauge

So my temp.gauge is being very weird ha. I don't know if its giving me false readings or not. It runs hot then cold. Then hot. Its weird. I've replaced the temp sensor In the intake manifold and the one for the temp gauge... Please help

Are you absolutely sure that you have purged ALL of the air out of the cooling system?

Only the sensor near the thermostat is involved in the gauge reading.

I believe I have. What is the best way to purge it? It only has been recently acting up. New thermostat temp gauge sender and choke sensor. The over flow is 3/4 full and last time I checked the rad like 2 days ago it was full. I checked when it was cold

I purge mine by jacking up the front end, taking off the cap, and running for 20 minutes, topping off as necessary. The only other thing that comes to mind might be the wire intermittently shorts out, causing high readings, then drops down.

I think the shorted out wire might be the issue my cooling system is top notch that's why I was skeptical. I have a 3000 cfm flexalite fan.. How can I check for a short?

How are you controlling your fan? Temperature sensor in the rad? Maybe your temp is increasing, then the fan comes on, and cools it back down.

Yes a temp sensor in the rad and I have a manual override switch in my truck. I'm using a flexalite adjustable relay.. It cools very well that's why I don't understand it getting this hot.. Hopefully its just a shorted out wire..

Just a share on my truck.The temp would climb up but then drop back more so in hot seasons and the fan worked fine.I def found running the ac it would do it more especially if sitting in traffic.My gauge never went half way but would fluctuate.I will say once I upgraded my radiator and heater core and associated hoses,and intake gasket and those 3 hoses for coolant under the intake temps stayed low.If your still running a oem radiator and heater core they both may be restricted in coolant flow and or a water pump that needs a update due to age.Not saying the wiring is a possible just some info that these trucks do have wacky temps going up then back down for no apparent reason.My guage reads a 1/4 period from cold even when 95 or say 35.

I would like to know: what is the point in jacking the front end up while purging?
I'm just curious not trying to challenge you.

I use a block of wood on my floor jack, and use the big cross beam under the engine, like half-way back. Do NOT jack up near the radiator !!!