Solved cracks in a print

You will need to extrude ABS very hot, it should be as hot as you can get it to print before it starts bubbling. What you are seeing is weak intra-layer adhesion.

 

Also, just to make things interesting, because ABS likes to warp it can do similar things to what you show when it cools.
However, @WheresWaldo is more likely correct if this print was fine initially and then cracked much later it is simply poor layer adhesion.

 

Well, II haven't used ABS in a couple of years, but that seems a bit on the low end.
I figure you used a temperature tower or the like to find your sweet spot and if that is it, then it is what it is.

https://www.thingiverse.com/thing:2318636
or
https://www.thingiverse.com/thing:2493504/#files

or something similar

 

FWIW I use ABS on my Zortrax machines daily and I push somewhere around 260-275. Granted the zortrax runs hot and with a perf plate on the build so figure a good "starting" point would be to up it to 250 on the extruder, test print and see how it looks. No cooling fans.

ABS is quite like PLA as far as dialing it in for strings and print quality so just do the normal after that 250 print test. Its not abnormal to run as hot or hotter than me depending on the ABS. (its a nightmare, since I have to run it I bought a machine that CAN out of the box )

If you dont already pick up an enclosure for your machine to help keep the heat in.