start with the basics and just replace the overflow rad cap. Mine had the same issue and that was the problem. and it is just a couple of bucks.
Yes it could be the water pump. It could also be a clogged radiator, or air in the system that needs to be bled. out, There is a bleed screw on the thermostat housing. With the engine running unscrew the valve till coolant flows steady with no air pockets for at least 5 seconds. Now there is no air in your system. Don't let your coolant get too low or this is what will happen.
The coolant is pumped from the thermostat housing into the top of the radiator but not until the thermostat opens.
There could be several answers to that question. The thermostat could be stuck closed. The reservior could be overfilled. The cooling fan may not be working. The radiator could be stopped up.
In the engine compartment, on the left side of the engine is the coolant reservoir. In the coolant reservoir, there is a sensor at the bottom of the reservoir. This sensor is supposed to let you know when you are low on coolant, but can also become defective, and give you a "false-positive" reading. The only way to know this is to check your coolant when the low coolant light comes on. If there is a significant decrease in coolant, you may have a problem in the cooling system , but if you don't, chances are the sensor isn't working. If the sensor is the problem, you can unplug it from the coolant reservoir, by unscrewing the two screws holding the reservoir to the car's inside firewall, then tilting the back of the coolant reservoir forward until you see wiring coming from the bottom of the reservoir, which is the plug for the low coolant sensor. Unplug the sensor, and the low coolant light won't come on anymore. However, you will now have to make sure you check your coolant level in the reservoir on a regular basis.
The hose coming from the thermostat housing connects to the upper part of the radiator and allows coolant to flow into the engine...
It probably has a leak. Here's something to check - the radiator has a tube coming out to the reservoir, so when it gets hot and expands the coolant goes into the reservoir and should go back into the radiator when it cools, but if your reservoir has a crack and the coolant leaks out, well it's gone and can't go back into the radiator - this would cause a lot of loss of coolant.
It's in the thermostat housing between the actual thermostat and heater hose. Has a little insulated wire coming out of it.
That is the overflow hose. It comes out at the level of the cap to allow for any extra coolant to escape.
There is a sensor located at the bottom of the coolant reservoir.
I am currently addressing the same problem with this car for a friend. I found a pressure leak at the seam between the metal coolant cap neck and the plastic coolant reservoir. New tank over $50 from aftermarket online, got one of many at the local junkyard for $5. 20 minute job. The coolant leak continues, however. I think it is coming from the heater hose; will confirm tomorrow. This car has had 2 replacement water pumps; about 120k miles.
disconnect the hose going to the radiator plug the hose coming from the engine side and flush with a garden hose
Overheating due to coolant going to the reservoir and not coming back to the radiator because of the bad cap.