Air in coolant system

[james250]

If the expansion tank becomes empty or very low can air enter the coolant system? I need to bleed my system as I'm sure there is air in the system because I hear the sound of water travelling. I don't see any visual leaks anywhere and water pump was changed about 60k miles ago. The expansion tank looks very low I need to see if it's actually empty or very low. It's hard to tell with the container as it isn't very transparent 

[TDP]

Yes it can, happened to my SC recently. The solution is to top it up - you will probably need to top it up several times from the radiator, running the engine in between, eventually the coolant will replace the air in the system. Remember not to take the top off when the system is hot!

[is200 Newbie]

Yes it does (+1 to Tobys answer) You usually hear it from the foot well but i would question why it is being lost - is there a white crust around the water pump?

[james250]

9 hours ago, TDP said:

Yes it can, happened to my SC recently. The solution is to top it up - you will probably need to top it up several times from the radiator, running the engine in between, eventually the coolant will replace the air in the system. Remember not to take the top off when the system is hot!

Top up the expansion bottle first then top up from the radiator cap when cold?

@is200 Newbie no white crust near waterpump. 

[is200 Newbie]

1 hour ago, james250 said:

Top up the expansion bottle first then top up from the radiator cap when cold?

@is200 Newbie no white crust near waterpump. 

There should be no reason that you cant just top up the expansion tank as it is part of the system - water will circulate through it - remember to use the correct coolant. How low is it or is it actually empty. If filling it up it might be an idea to note how much you need to fill it by and keep a record of further top ups - it should not disappear

[TDP]

My mechanic recommended doing it via the radiator but I don't think it matters where you top it up.