I will agree that 90% of the time I don't have issues either, only one time did I have to jack up the front end and do this and I burped my system for almost an hour before I saw that it was finally done.

 

One thing that may help prevent air grtting trapped in heater core, is to make sure your temperature control is set all the way on HOT before you do anything.

 

Unfortunately this does nothing to help on Montero Sports due to the neglect of the engineers in charge of designing the HVAC system. There is no heater core valve to control the flow of coolant to/from the core, the flow is constant. This actually plays a role into why so many people complain about poor AC performance on these trucks. I noticed a huge increase in cooling performance when I bypassed my heater core when it blew. Now this isn't to say having it on full blast doesn't have any merit, it does help to monitor the performance of the heater as you burp the system.

Edit:
I'm actually in the process of picking up supplies to make my own heater valve system. Using an old EGR control solenoid from another monty and a vacuum controlled heater core valve from Oreilly's. I'm awaiting my relays and electrical supplies from amazon and some free time to install it. I plan on making use of the unused vac port on the top right corner of the plenum to connect to the solenoid.

 

Thank you for reminding that Sport is often an entirely different animal from full size Montero. Not all experience with one style translates directly to the other.

As far as making your own HVAC controller - have you considered using an electrically actuated ball valve? They make them in 12v version and I'd think it might be easier to control it with power supply than with vacuum. Just a thought.

 

When/If the solenoid fails I'll consider switching over to this, but unfortunately I already have purchased everything. I'll let y'all know how it turns out.