Over the years, I have seen overheating caused by radiator leaks, a bad water pump, and a stuck thermostat. The vanes on my aluminum water pump were completely gone because I did not change my coolant. My heater core was also completely clogged up so I replaced that too. I bought some radiator flush and flushed out the cooling system before I replaced the coolant.

A very quick overheat and no warm coolant going thru the radiator is usually the sign of a stuck closed thermostat.

Get this fixed immediately since these engines are prone to head gasket failures.

Could just be the thermostat do you have a hole in your radiator or a cracked cylinder head

The bottom one is usually gunna be a tad cooler. After all the coolant runs through the rad to get cooled and goes back through the engine. It may be your thermostat, waterpump or an airbubble in the system.

#1. Buy a new thermostat from the dealer of the car and change it. Always use dealer only antifreeze to fill the system. Discount store antifreeze does mix with the factory long life chemical antifreeze.

#2. When was the last tine that your cooling system was drained, flushed and CLEANED with one part powered acid cooling system cleaner to get the corrosion, rust and slime out. If anyone had ever dumped discount store antifreeze in any cooling system built during 1995 and after it will need to be CLEANED.

The bottom hose should be as hot as the top hose, If not your radiator might be plugged.

I have a 1998 Subaru Forester that's been overheating ever since the weather warmed up. The a/c doesn't work but the heater works great. It overheated maybe once over the winter but I topped off the coolant and it was fine. It heats up within a few miles of driving and I'm not sure what to do. I checked the bottom hose and it doesn't seem to be getting hot. Could it be the thermostat even though the heat works fine?