Genuine GM (12378255) Fluid 3634621 Cooling System Seal Feb 03, 2018I had a coolant leak on the rear bank of my engine (2008 GM 3 V6). The leak could be seen under close examination, and could *definitely* be smelled - even with the hood closed. Fearing the worst, I crushed three tablets in a ziplock bag with a hammer, and emptied the contents into the cooling 4.4/5(206)Price: $6 | Repair Guides | Fluids And Lubricants | Cooling System Failure to use the engine coolant supplement (sealant) and the approved coolant antifreeze could result in major engine damage. When refilling the engine cooling system, add three pellets of engine coolant supplement sealant, GM Part No. 3634621 or equivalent and coolant antifreeze meeting GM specification 1825-M.