Is this waterblock usable without problems

Solution
It looks okay and you should be able to take it apart to make sure. The main section over the CPU area looks good and it would not hurt the CPU if you fitted it and ran a few tests to see what temps you are getting. Make sure you clean and flush it first...
It looks okay and you should be able to take it apart to make sure. The main section over the CPU area looks good and it would not hurt the CPU if you fitted it and ran a few tests to see what temps you are getting. Make sure you clean and flush it first...
 
Solution