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Vacuum Method for Refilling Engine Coolant
A coolant refill is an event during which the protection of components from damage caused by boiling coolant is easily overlooked. It is important to understand that the procedure used to refill the system after draining the coolant can create air pockets. Air pockets commonly form in the EGR coolers, which results in portions of the coolers sustaining damage from hot spots where coolant has boiled or there is no coolant. Original equipment manufacturers (OEMs) recommend the use of coolant refill equipment, which completely evacuates the cooling system of air and pulls coolant back into the engine using negative pressure Figure 18. A coolant refill/air purge tool is typically air operated. The tool first uses a venturi and compressed shop air to draw a vacuum in the entire cooling system. A vacuum ensures that no air pockets are in the cooling system while refilling. A coolant reservoir holding the coolant charge is then used to draw only coolant into the cooling system using the service tool, blocking unwanted air from entering the system. A pair of hand-operated valves are used to switch the tool from drawing out air and establishing a negative pressure in the cooling system to filling the system with liquid coolant.
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Technicians Tip |
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Core plugs—or frost plugs—are used to seal passageways in cylinder blocks and head castings designed to flush sand from casting after manufacturing. While these plugs may be displaced by frozen coolant, they are not designed to prevent engine damage. |
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FIGURE 11-18: A coolant refill/air purge tool uses shop air and a venturi to pull a vacuum into the cooling system. Next, a hose is dropped into a container of coolant, and the cooling system’s negative pressure draws in coolant, which fills all spaces and voids with coolant.
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