Why is my van still over heating after changed thermostat

I am having a similar problem. Looks like a clay mud substance in the coolant tank when empty. Have to put water in it constantly. The water used to help but now it still gets pretty hot. We do not have the money for a huge repair and also don't know anyone who can help outside of a garage. Any advice on a cheap/ temp fix is appreciated. We are hoping to get another vehicle in September.

The "easiest" way to service the vehicle yourself is to make sure the thermostat is out then put back together. Disconnect and take the top hose off the radiator(this is the hose that returns the water). With the thermostat out and the hose off of the radiator, start the vehicle then take a hose and run it in the hole the hose was connected to. Run the heat on high while doing this. Be sure to point the hose from the motor away from your belts and yourself. This will flush the system. Run the water until it comes out clear from the upper hose. Turn off the vehicle and after cooling down, re-install the thermostat and reconnect the upper hose. Refill the radiator with water and try driving it too see if it overheats again. If not, then drain the radiator and put in the proper mix of anti-freeze and water or premix (your preference or recommendation from manufacturer). If you mix it yourself, please use distilled water. This is the most you can do without having it serviced.