ISTA shows adding the coolant first via a vacuum system and then doing the bleed procedure. Is the vacuum step really necessary and how many times did you need to run the bleed procedure? Seems to me the bleed procedure will clear airlock so the vacuuming is more for a leak check?
I never used any vacuum step. Normally running the bleeding procedure once should be enough. But you will see, when the water jet going back into your coolant expansion tank is steady, you have no more air. When you have air, the water jet will be interrupted with air pockets on and off. So if you still have air, you can always run it twice, there is no down side of doing so, beside about another 10 - 15 min.
ISTA shows adding the coolant first via a vacuum system and then doing the bleed procedure. Is the vacuum step really necessary and how many times did you need to run the bleed procedure? Seems to me the bleed procedure will clear airlock so the vacuuming is more for a leak check?
I never used any vacuum step. Normally running the bleeding procedure once should be enough. But you will see, when the water jet going back into your coolant expansion tank is steady, you have no more air.
When you have air, the water jet will be interrupted with air pockets on and off.
So if you still have air, you can always run it twice, there is no down side of doing so, beside about another 10 - 15 min.