Rule So Hard

While working on my truck I realized that due to the rear heat on 4 runners it seems Toyota added a lot of extra cooling lines. This IMO is pointless and creates a lot of extra high area for the air bubble curse to take place. So I decided to eliminate all these lines and run my heater core backwards.
I reasearched the topic and didn't find any thing similar. My heat works better IMO after this. My heat would cool down while driving and I suspected it was a air bubble but I failed at many attempts to purge the air. My heat works great now.

Benefits:
-less complicated system to diagnose.
-less area for air to be trapped.
-easier to access coolant sensors near firewall.
-allows installation of a purge hole in the highest point of the cooling system.

Down falls
-Lose rear heat (could be installed easily if wanted)
-Lose heater valve
-I speculate that if you broke a engine mount it would rip one of these lines away. They are very short afterwards.

If people actually like this idea I have pictures and can make a write up on it.

Gevo

I don't fully understand the need for this to be honest. With fully functioning heater cores there is no reason air bubbles would get trapped. I ripped out my 4runners existing hard pipe coolant lines to the rear heater and installed hoses instead (they were clogged), and after a new radiator, rebuilt engine and new main heater core, I have no problems.

Maybe I am not understanding the problem correctly, you are saying that you weren't getting good enough heat through your main heater core, and you rerouted the lines and cancelled the rear heater and now you are getting better heat?

Rule So Hard

I did it mainly to simplify the system by eliminating unneeded connections and length of hose. The lines run to opposite sides of the engine bay for what seems to be only for the rear heat. I can't see any other reason for them to be routed that way.
Many cooling systems are prone to getting air in the system if it gets low or the system is drained and re filled. From what I've read the 3vze falls into this category.
I eliminated the rear heat because I read the lines are prime to rusting away. So until I can replace the lines with rubber ones.