[quote=”nightflyr” post=204305]Still comes down to if the system is purged of air and completely full.
Then after a time you have air introduced.
You either are:
Taking combustion gases into the cooling system.
Or drawing air externally into the cooling system.
Now if a combustion gas test yields a negative result your left with a external leak with in the cooling system.[/quote]
I’ll throw this out — What about the thermostat?
Is it possible for air to enter the system when the thermostat moves its valve?
Anyone heard of that?