Why is temp gauge shooting up. The radiator water level is low. on 2004 Toyota 4Runner

I own a 2004 V8 4runner. Its mileage is about 38k. I was driving when I noticed the AC blowing warm air. I checked to see if the heater was on, but it was off. I switched off the AC, and drove home. When I turned off the engine, there was this hissing sound(like gas is being released) that lasted about 1 minute, coming from behind the engine. The next morning, I checked the radiator water level, it was quite low. I refilled it and also noticed the coolant container was empty. I cranked the engine(with the radiator not covered) it came on smooth, but within seconds the radiator started foaming. I covered the radiator, drop the hood and drove off , the Temp gauge was at running level(i.e. somewhere at the middle). After driving(with the AC on) for about 10mins, the gauge shot up towards the red mark, I turned the AC/ engine off and left it to cool off. When I drove off again, it took about 2mins and the gauge was rising again. I noticed that if I Moved faster, the gauge came down. I would like to get some expert advice on what the problem might be and what solution to proffer. Thanks in anticipation

by in Portsmouth, VA on May 23, 2012
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1 answer 1 comment
ANSWER by , May 23, 2012
i would start by pressure testing the cooling system to find a leak. sounds like poss a hose. also have it ck'd for headgasket issues also.the temp issues sound like an air pocket
COMMENT by , June 01, 2012
Thanks. Went for the pressure test, and we found a leaking hose!