The test rig was designed and built to determine whether it is possible to objectively measure the effect of coolant composition on the performance of engine coolant pump seals. The rig uses a standard, current production, mechanical seal. A low silicate U.S. made coolant for baseline tests was selected. The effect of increased total dissolved solids (TDS) will be determined by adding twice and four times the normal recommended level (3% by volume) of supplemental coolant additive (SCA). Shakedown tests with the low silicate coolant were successfully completed. Leakage and wear characteristics observed on the baseline tests were used as a reference to evaluate seal performance in coolants containing SCA.