Planetary Protection (PP) is the practice of protecting solar system bodies from Earth life and Earth from possible extraterrestrial life forms. Spacecraft surfaces are cleaned and routinely sampled to determine the bioburden and ensure compliance with PP requirements. Bulk materials, like adhesives, are destructively assayed, or a NASA specification value in lieu of direct sampling is applied, to estimate the bioburden. Currently, no specification value exists for liquids. The closest analog is the assumed value of 30 spores/cm3 for non-electronic solid materials; however, applying this assumption to liquids is problematic, as it can lead to a substantial total spore burden that rapidly consumes the allowable bioburden margin for a given mission, particularly when large volumes are involved. CFC-11 (Freon) is a refrigerant commonly used in spacecraft to provide cooling for the Heat Redistribution System (HRS). The HRS Mechanical Ground Support Equipment (MGSE), designed for the Europa Clipper spacecraft, delivers CFC-11 to the spacecraft. The system utilizes three 2.0 µm filters. This design is markedly different from the Mars 2020 and Mars Science Laboratory mission, which utilized a 0.2 µm filter specifically to remove spores, which typically have diameters around 1 µm. Thus, an analysis was required to measure the bioburden of the CFC-11 for the Europa Clipper HRS. For our study, we used 90 mm Millipore filter holders that were connected directly to the HRS MGSE system. In total, 3 L of CFC-11 were flowed through the filter holders. The 90 mm filters within the filter holders were processed using the NASA Standard Assay, with membrane filtration as the culture-based technique, to enumerate colony-forming units. Using these experimental results as one of the inputs, a probabilistic mathematical model of the CFC-11 and bio-load transfer process was developed to provide a predictive probability distribution of the number of spores transferred to the HRS and ultimately substantiates that a 0.2 filter is not necessary within the system to lower bioburden, a feature that saves the project significant time regarding fill operations. This probabilistic mathematical model may be used to inform the MGSE design for future missions, such as the Mars Sample Return Sample Retrieval Lander, regarding the choice to replace the 2.0 µm filters with 0.2 µm filters. This study recommends a mean value of 0.04 spores/L of CFC-11 transferred into the Europa Clipper HRS and for future missions that intend to use the same HRS MGSE design.