Water of backup package decreases daily
 

Hello everyone,
I have Accent 2017, I got overheating many times, I found that the cause is the thermostat, I removed it and now the heat is normal.
Now, I have another problen, the water in the backup package decreases gradually, about every 3 days I have to fill it with a approximately cup of water.
Any solution please?
Regards.

"backup package"??
Do you mean the coolant overflow reservoir??

Removing the thermostat and not replacing it is only a temporary fix.
In the winter months, there will be no heat. Engine will take forever to warm up.
Fuel economy will suffer.

The proper thing to do is to find out what is wrong and fix that.
Sometimes the radiator needs to be back flushed to remove particulates
This reduced heat transfer also happens to the heater core sometimes.
Sometimes the radiator needs to be replaced.
But, before doing anything else, should do a few tests to see what is exactly wrong.

Is the fan turning on? Is the water pump pushing the water through the system?
Is there enough coolant in the system?
Is the radiator working ?

If you feel that you have fixed the car and just want a solution to the disappearing cup of coolant every three days
Then, the only thing to do is to fill it up every three days. Sorry.

Older engines were a ton of iron and overheating didn't do as much damage as it can do to today's engines.
So,,,, how badly did it overheat and for how long. If the engine ran hot for even a short time it can do damage that will not show itself right away.
Coolant loss is something that should be checked out as soon as possible to hopefully prevent future problems.

Leaking head gasket....or a leak in the cooling system. Check hoses and radiator for drips.