Coolant bleeder for the Mazda5 2.3 MZR?

I recently replaced the thermostat on my wife's '07 Mazda5 because the check engine light came on. The system is full right now, but there is no heat coming out of the heater core. Is there a specific bleeding procedure for these? I right now have tried idling it for 20 plus minutes twice with the front end raised, and still no heat in the cabin. I know my '06 Ford fusion with the Duratec 2.3 has a plastic bleeder screw on the driver's side of the engine hose cluster, but i cannot find one on my wife's Mazda. One thing I noted when replacing the thermostat is that the aftermarket unit had the air bleed valve/hole at the side instead of the top like the oem one did. The aftermarket thermostat is a different design, and I was able to rotate the air bleed hole to the top of the thermostat like the oem one after compressing the spring. Other than that it was fairly similar to any other thermostat I have replaced. I am scratching my head at this one.

The one thing that confuses me slightly is that this has a radiator cap and an expansion tank. Do you run it with just the cap off initially to bleed the air out, or does it automatically bleed it out of the system via the tank? I am trying to think back to when I had my Ranger that had a similar setup (a radiator cap with a non-pressurized overflow tank). After it cools down, I am probably going to try and run it with the radiator cap off and see if that does it.

Apparently, the radiator cap has to be off before you start the engine to bleed the air out of the system. What worked for me was letting it idle with the cap off while topping off the radiator. Then I would squeeze the thermostat hose multiple times and watch for air bubbles until they all worked themselves out and I saw no more. (Be careful though, it's really close to the serpentine belt!) Then, I put the radiator cap back on and had the throttle up to 2500 rpm for a couple of minutes until it was up to temp completely. The heat started coming out of the heater core like it should after that.

This was a bit of a frustrating job overall. When putting the belt back on the OEM tensioner, the left hand threaded bolt snapped off of the tensioner assembly, effectively destroying it. I had to wait more than a week to get a Gates tensioner assembly. I did notice that the bearing was toast in the tensioner pulley, but the $12 would have been alot easier to swallow than the $88 I paid for a new tensioner assembly. Why they made the boss for the M10x1.5 x 25mm long bolt so thin, with very little threads actually extending into the tensioner body, I have no idea. I didn't pull the Gates 38357 replacement tensioner apart to see if it was an improved design, but I did note that the spring housing is much smaller than the oem one. I would hope that the bolt extends a ways within it.

I also replaced the serpentine belt and the stretch belt for the AC with Gates belts. I even ordered the (supposedly) OEM specific stretch belt installation tool, and found that it did not fit the crank pulley. I needed to modify it to get the stretch belt on. I was a little disappointed to find out it was made out of aluminum as well. It doesn't look like a tool that would last more than 3 or 4 installations, but I could be wrong about that. I hope I am.

At least draining the coolant gave me the excuse to replace the cartridge filter assembly and swap it for a spin on unit. I am glad to be rid of it.