Water is coming back up through the plastic box where you put the water but car never over heats? A friend said it may be a thermostat sticking but I dont know. Nothing leaks around radiator or hoses or any other area. It leaks the most once I turn the car off.

sticking thermostat

Methods to trouble shoot
(1) check thermostat device. if thermostat is stuck - not working half the water used in cooling system is missing once engine heats up which can lead to over heating. (may need mechanic to check this)
(2) check radiator has water in it . if it is low there may be a leak in cooling system somewhere check rubber hose and radiator are not leaking.
(3) check fan belt is engaging fan in front of radiator
(4) if electric fan check if fan activates once car has heated up
(5) check oil level of engine on dip stick. If low oil add some oil and re check oil dip stick. DO NOT PUT whole oil pack in (don't laugh I know someone who did this and has to go to mechanic and get oil removed)
(6) if rubber hoses blow off connectors then you may have a broken head gasket seal. A pressure test of the radiator will confirm this.
(7) Possible water pump failure. Check by taking cap off radiator and run engine see if water is flowing in radiator and test if water is heating up in the radiator. Remember to put cap back on radiator when finishing test.
(8) check if bubbles or oil are in radiator water this could indicate a blown head gasket problem also.

THE thermostat could be stuck shut,take it out ,try the thermostat in boiling hot water to see if it is opening,or itcould be a headgasket,look to see if there is water on the dip stick

if the thermostat came with a new rubber o ring that fits around it, then no the plastic housing shouldnt need to be sealed, but if there is no rubber o ring yes seal it or it will leak... as far as distilled water, no just reg tap water is fine...remember to put anti-sieze on your bolts before you put them back in.. or they may not come out if you need to replace the thermostat in the future... hope this helps

Your thermostat is probably stuck shut. When the car is cold, open the radiator cap and fill the radiator to where you can see the coolant. Start the car and have a friend watch the gauge rise as you watch the coolant. At a little before or right at half way the thermostat should open and you should see the coolant drop. At this point the car should also have heat. If you can not see the coolant drop it can be one of 3 things.
Thermostat stuck shut water pump is bad blockage in radiator or cooling system.
Heres what I would do to rule out water pump 1st. Disconnect the line that goes from the water pump to the engine from either side, the pump or engine. back away and start the car. You should see coolant coming out of the water pump. if you dont try to put water into the hose to make sure the water pump has water in it. It could be empty if the pump is after the thermostat and it is stuck shut. If the water pump has water in it and nothing comes spraying out when you start the car, the pump is bad. If it does come out you need to remove the thermostat and push against the wafer in it on the opposite side of the spring and see if it moves. If it does not moves (wont be easy) the thermostat needs to be replaced.

sounds like your thermostat has stuck open, replace the thermostat and make sure the cooling system is full of coolant that is 50/50 mix of water and antifreeze

Hi,
It turns out the cars thermostat is sticking, as the engine gets hotter, the ac kicked out. Some sort of sensor turns off unnecessary stuff (like the compressor) to save it. I changed the thermostat, and no more problems. Let the car sit in your driveway idling, ac on. If the ac goes off, spray the radiator with water, and see if comes back on; then it's the thermostat. Another possible thing could be this air filter (cabin filter) is clogged. Usually it is located in the plastic duct work in the car behind the glove box. The filter was put in newer cars to filter out pollen, etc. getting into your car. I would check the cabin filter first. Either blow it out with compressed air to clean it, or leave it out. A new filter runs about $40 and it's a dealership item
Thank You for using Fixya.com

Need to check your radiator flow, and thermostat, start the engine cold, with radiator cap off, watch for the water in the radiator, when it starts to bubble over let it, keep water hose close, radiator should blow back till the thermostat opens, the water will go down, and add more water if needed, and put the cap back on,,,, if your thermostat is stick closed it will cause over heating......and you may have to have it replaced.

there could be an air gap in you coolant circuit, make sure you have purged the entire cooling system of air that might have been be trapped in the cooling circuit when you changed the T-stat.

What temp thermostat did U put in????? Check and see what thw manufacture call for you car. Also check to see if any leaves are in your heater box, which is stopping the air flow. Some cars have and air filter on the inlet duct. It could be plugged. Check this out also.
Take the 2-heater hose off where the water goes into the heater coil. Back flush it with your home water hose, the oopposive direction that it normal goes. It can get stop-up. You can also flush your whole system by empting the radiator and put a can of old time comet into the radiator, and fill it also with water, let it run for 1-hour, the empty a,d fill with water 2 more times. Fill it back with antifreeze and go with it. This should clean everthing.