[Razorback1980]

Water pumps are a shaft driven impeller. The only way they do not pump is if the impeller is not connected or slipping on the shaft which is almost never. The slipping of the belt is a possibility, but I'm hoping your timing belt is not that loose...otherwise you will have bigger problems like bent valves. The higher the rpms the faster the impeller turns which circulates water better of course the law of diminishing returns does apply here. The most common way water pumps cause overheating is the seal starts leaking coolant past it and it runs out the small hole in the bottom of the pump causing your coolant level to go down. When you are feeling circulation in the hose, you are actually checking the thermostat to make sure it is open and allowing coolant to flow through the system. One other thing to always check on the water pump is up and down play on the shaft to make sure the bearing is good. If the shaft moves up and down, the seal will leak and you will lose coolant. Fans are very important, pay very close attention to them. They don't wait until the car overheats to come on, they come on at a certain temperature and since your car cools better at high rpms which translates to your car moving faster, the problem is probably with your fans. Make sure they work the way they are suppose to and make sure they both work. They are critical to the cooling of the 944. Considering that yours is going high on the gauge and then the thermostat opens, that makes me suspect the thermostat is at least partially the problem. They are cheap, replace it. Next make sure both fans work and work properly. Check Clarks-garage to test these. The third thing to check is to make sure your gauge is reading correctly. I use a thermometer on the engine to read the temperature and see if it is relatively close to the same as my gauge.