Preventing air bubble when changing coolant

[Bob Ellithorpe]

What if anything can I do to prevent getting an air bubble when changing coolant ??

 

[Bud Fox]

Bob,

when I change my coolant, I leave the cap off, turn the heat on, and bring the motor up to about 1500 rpm. Once the theromostat opens and it starts to circulate, the air pocket usually appears and then I top off in radiator and fill overflow. If i understand your question correctly, I hope this helps

 

[Bob Ellithorpe]

I guess my definition of an air pocket would be a bubble of air trapped inside the engine or heater . I would assume that if you could circulate the coolant while filling you could avoid this.

 

[The patriot]

I dont think that's possible with this truck. The rad cap is at the highest point in the cooling system.

If in doubt, what rednut said is what the mercedes dealer told me to do when I flushed it.

eric

 

[Missouri Mule]

Bob,

There is an air release valve near the thermostat. When engine is shut down it is open when engine is cranked up it closes.

This valve should keep air bubble from forming in engine when filling/adding coolant. This is why service manual states not to add coolant with engine running.



My Dad used to own Renualt 16 had manual air release valve on top of engine. When refilling/adding coolant if you did not open valve the coolant would burb back at you. But this radiator was lower than engine.

 

[DieselDoghouse]

Coolant bubbles

I musta been late for class... I always thought with the Cummins B engine your were supposed to fill the system shut down. the bypass loop (unless its clogged??) and the 'wiggle valves' on the thermo are supposed to percolate the air out as the coolant sinks. There was something in the manual about running the engine would defeat this. Anyway, I have always just taken my time (large coffee black, please) and never run into an airlock or underfill problem. Just lucky??