It doesn't work when i connect it to a power supply, and makes weird noises. Also when i rotate it with my fingers it makes noises, different than other motors that works fine. Is it burned competely or can i still repair it? I use simple arduino yellow motor from 4wd platform.
Hi,
It does sound like you have a problem motor.
But you really are not giving us very good details.
Let's start with the motor. Can you get a link to the product you purchased?
Did the motor ever work? Like it worked for a while and does not work now. Or has it failed every time you tried to use it?
Yea sorry, i should give you that information earlier.
platform with motors: Chassis Rectangle 4WD 4-kołowe podwozie robota z napędem Sklep Botland
All 4 motors worked perfectly. I took the robot outside and switched on, it suddenly rode on the grass and the engines stoped for a while. Now 3 works and 1 is not
I see. 4 motors each in a gearbox.
Do the motors slide out? Is it the motor that is bad or the gearbox?
I did some poking around. Those look a whole lot like these gearmotors from Sparkfun.
The motor makes noises when i turn the wheel and it's turn off. When is turn on (i use ROMEO V2 board) it doesn't roll, maybe something is blocking mechanism in the inside, becamuse when it's on and i want to turn it with my hands it's about to move but don't.
Can i try to open it up?
Open it up - its probably burned out or perhaps the gears have broken. If you'd been running them for a long
time I would suspect worn-out brushes, but that doesn't sound likely in this case.
Motors take 5 to 20 times more current when stalled, leading to overheating usually.
I opened it up. There was something like that- motor - https://www.google.pl/imgres?imgurl=https%3A%2F%2Fcdn.instructables.com%2FF29%2FFRIU%2FIC0VE8X4%2FF29FRIUIC0VE8X4.RECT2100.jpg&imgrefurl=http%3A%2F%2Fwww.instructables.com%2Fid%2FHow-to-drive-a-DC-Motor-with-Transistor-Arduino-Tu%2F&docid=7ZVkAqOI4C3LMM&tbnid=8BD0Qwg-VpNb_M%3A&vet=10ahUKEwj-1qX6uMzVAhWEHsAKHdIECxsQMwhYKCgwKA..i&w=1296&h=1080&bih=696&biw=1517&q=dc%20motor%20inside%20arduino&ved=0ahUKEwj-1qX6uMzVAhWEHsAKHdIECxsQMwhYKCgwKA&iact=mrc&uact=8
and plastic gears. Motor moves but the gears not connected to it. I can not descire it in engilsh well. Motor wasn't connected properly to a gears. Propably it loosened during work. Now it works thanks!
If the pinion was slipping on the shaft, it will happen again and probably get worse.
Maybe take it apart again, pull the pinion, clean the shaft and pinion with IPA or alcohol, and
superglue it back on (careful not to get the glue on the pinion teeth).
I've done it several times, like you sad it had broken again. I glued it with hot glue pistol. If it break down again i will clean shaft and pinion. Thanks
hot melt glue will not work at all, as it doesn't chemically adhere to metal.
superglue does work with metal, but its still a bodge.
Propably with superglue i will get much more thin layer of glue. When it will break up again i will do it, but... I've done my project - obstacle avoiding robot and now it just Standing and getting dusty on my desk 
I will test it once again tomorrow and i'll call you back