HELP! 99 obs temp gauge not working right.

Howdy. So, the other day I started up my 99 outback sport to head downstate for the week and my temperature gauge started to climb rapidly (approx. 5 sec). It sat there for about 10 seconds, then made its way back down to normal temp. I pulled over to check things and there was no coolant anywhere, no smoke or steam coming from the engine, I could even put my hand on the radiator cap. It was warm like a car that had been running for a half hour, but not hot like I would be if it here over heating. I kept an eye on it as it fluctuated from pinned past the H, back to normal temps, then back up the whole way to Presque Isle. I got some coolant, topped off the radiator to make sure, and then let if run with the radiator cap off for about 10 minutes. This seemed to fix my problem. I drove home 250 miles, made it through the NEFR without a problem, and headed home tuesday, still without issue. 10 miles before my exit it started to climb again, sit for a few seconds on the H then drop back to normal temps. It has been doing it since. The engine isn't showing any signs of overheating. It doesn't even smell a little hot. I have no idea where to go from here. Could it be my temp sensor? I also have been having an issue with my gas gauge dropping, gas light coming on, then going back to its normal position with the gas light off. Could it be my guages? Or are they unrelated? The interior/gauges are from a 99 2.5, my engine is a 04 2.5 forester engine block with all my 2.2 stuff bolted on. I would really appreciate any input. I've lost one engine, I don't wanna lose another.

Hmm. Hard to diagnose without being there in person BUT.. it could be you have a slight coolant leak somewhere that is allowing air into the system. It gets airbound, isn't circulating right, and the temp spikes. The temp sensor is on the crossover pipe on top of the engine, the best place to feel for yourself the current coolant temp is on the upper radiator hose. When it's airbound, it can be burning hot on the upper hose and room temperature on the lower hose and at the cap.

OR, since you have stated gauge issues, it could be the cluster itself I think. Especially if the engine really ISN'T too hot. Also possible the temp sensor can go bad.. but not usually in the way you describe (that I've heard of anyway).

Was the coolant actually low when you topped it off in Presque Isle?

The radiator only took about 3/4 of a quart... not really enough to make a difference. The engine isn't showing any signs of over heating and doesn't seem to be hotter than normal..I'll check the hoses as you mentioned