This is going to be a long "introduction"
My sentra b13´s engine overheated yesterday, the fan didn´t work out, so I tested it directly to the battery and it is working fine, also the circuit is working fine, checked the fuses and they were ok, how can I test the thermostat? As the engine overheated, it started a leaking by the water pump, what is the cue to fix it?

Help on an overheated b13 engine.

E-mail me about an overheated b13 engine to rodripin@hotmail.com

You do realize that you only need post once in the correct forum. There are two posts in the introduction forum stating that it is for INTRODUCTIONS. Anyways, give this thing time, people will respond.

Well to be honest its kind of a waste of time to test your thermostat. Reason is because you have to pull it and put it in a pot of boiling water to see if it pops open. I say for 6 bucks buy a new one and some rtv thermostat housing rtv (a few extra) and just change the thermostat out all together. If you insist on testing it just be sure to have a thermometer to put in the boiling water to see if it opens (if at all) at the proper temp. Also some water pumps are manufactured so that when they start to leak (or weep) then that means they are shot.
If you are sure of the fan kicking on, and by the way I would run it up to temp and see if you can hear it come on, start at the thermostat because it is easier than the water pump. good luck

Thanks jer28usa!!!
Yeah you are right the thermostat has nothing to do with the fan, I found out that there is a small thing -I dont know what is the name of it in english- wich activates the fan, I bought a new one for 8 dollars and the problem was solved, my worry now is the water pump, I have to check the water level every day and wait until I can put the water pump down and see what is wrong with it, I ask for the price of it here in Bogota, Colombia where I live and they charged me 35 dollars. It is possible and I hope that only the gasket was damaged, will tell you more about it later. Thanks again... Rodrigo