For the last 1.5 years, the pump has been running fine even though the rear seal wash was blocked. Then in September, we were having issues with our pumps and found there was leaking in pump B. We did a maintenance, meaning cleaning the pumps and changing all of the seals for pump A and B, as they all looked extremely used and dirty. The system was running fine for about one month until now. We noticed some RT shifts in our samples and a higher baseline of noise, so we started checking our LC system. Both pumps failed the leak rate test, so we took apart both pumps, cleaned everything, checked the seals (which looked fine as they are quite new), and put it back together. At first the pumps could not get to pressure, so we opened the rear seal wash, and the pumps could get to pressure. However, both pump A and B kept having secondary leaks, or not being able to get to the required pressures for the pump leak rate test (but got quite close, like 750 instead of 800 bars). We have taken apart, cleaned, and put back the pumps multiple times, hoping that once it will do the trick, always getting a step closer. Now, after a very long purge of the rear seal wash, we got pump A to pass the pump leak rate test, but then after going for lunch and coming back an hour later, it failed the test again. For both pumps, we typically notice that the leak comes from where the heat capillary meets the gold seal between the primary and secondary pumps. Does anyone have any suggestions of what to test, what could be the issues, or how to know if the heat capillary or the gold seal need to be changed? It´s strange that is happening to both pumps and that it occurs right after a maintenance.