Burping the Radiator to fix a pressure difference in radiator/heater core.
The gurgling sound, you may be hearing inside the cab, is air bubbles rushing through the heater core, and yes, the fill needs to be completed. With the engine cold, check the overflow bottle. The liquid will be its minimum level and should be above the “low” mark on the bottle. If not, add coolant until the bottle is half full or at to sligtly above the cold level mark.
Here’s whats supposed to happen. When the coolant heats up, it expands and should burp some some trapped air into the bottle. Then, when the system cools and the coolant shrinks, it draws fluid from the bottle into the cooling system, that is, if there is enough fluid in the bottle to keep the inlet/outlet in the bottom of the bottle covered.
After about 3 thermal cycles, the system should have enough air flushed out. After that, keep an eye on the coolant level in the bottle for the next 3 to 4 trips.
The “sealed” coolant systems on today’s cars vary in detail such that no one set of descriptions fit all. However, all sealed systems perform the functions described above. The mechanical details do vary. In some systems, the overflow tank is pressurized to the same level as the engine coolant, while in others, the overflow tank is vented to the atmoshpere.
This is what I’d do. With a cold engine, fill the overflow bottle to or slightly above its “cold” mark. Put the cap back on the overflow bottle. Warm the engine into its operating temperature range, then shut off and let cool. After cooling, refill the bottle. Do this until the liquid high and low level stablizes.
Be very careful! Do not remove the cap of a pressurized bottle if the coolant (engine) is hot. Upon release of pressure, the coolant can flash to steam and geyser about half of the coolant out of the system. You could get scalded, not to mention the ensuing mess. Let it cool until you see the coolant being sucked out of the bottle back into the engine.
Antifreeze can be purchased as full strength, or already diluted half water and half antifreeze. Look carefully at your antifreeze container. Do not dilute the already diluted antifreeze.
Post time: Jun-02-2017