The rebuilt racks are susceptible to two main factors. Age and the quality of the core and reman parts.
If a reman rack is coming out of a warehouse in AZ or say, MN, it’s going to be subject to 100*+ or -40* temps. If it’s something that’s been sitting around for a few years and the last one, the seals will have rotted out.
If it was just rebuilt with good or average parts and core, substandard seals will also turn it into a boat anchor in a matter of minutes or months.
If possible pressurize any reman rack before it’s installed.