Fantastic news.

Following this first flush, the temps hovered at around the 210 to 220 range at idle. Upon bringing rpms to the 2800ish range, the motor cooled down to 180 on the dot and held for a little bit before slowly creeping back up. To the 210 to 220 range. This is the coolest running and idle temp I have had since the issue started. By 20 to 40 degrees. Looks like things are starting to break up!

Despite throwing all sorts of parts at it (which I planned on over time anyway due to the age and mileage) I am happy it was just a simple blockage that initial flushing made worse. I will keep at it over the course of this week to get it where it needs to be. I will likely drop my 180 thermostat back in over the 160 as well. This truck does not see winters but 180 is a healthy regulating point that I use on my other three 3VZEs.

 

Whatever gets flushed out of the engine can plug up your new radiator. I've seen hot rod guys put a piece of a pantyhose as a sock inside the return hose temporarily to catch junk. I've never tried it myself though. I'm glad you're making progress.

 

Besides scale restricting the radiators flow, the most damaging obstructions are at the small calibrated coolant metering holes in the head gaskets themselves.
It is very difficult to clear such restriction or plugging in these holes.
Sometimes strong reverse flow flushing will clear them somewhat.
Other times, only head gasket replacement after clearing all debris in the system will suffice.

 

Welp, in the course of this I think the head gasket may have went. While the drained water was indicative of there still being some scale buildup, right before draining, the exhaust started smelling like the flushing liquid.

I refilled and bled the system after a light hose flush from the heater hoses and also did the radiator seperate. Now the temps rise very quick and i shut it down upon seeing 270. Guess ill be pulling the engine apart yet again.

 

I guess that block test suggestion wasn't such a dumb idea.
But sorry you have to take it apart again. I've been in your shoes. You just power through.

Just food for thought:
Before you take it apart I'd highly recommend getting as much data as you can, because once you loosen the head bolts There's no way to get that info.
I'd still do a block test.
I would run a compression test-at least a dry one.
And I absolutely recommend a leak down test. This one test will give you the most info of all.
Now you can begin a teardown with a focus of what you're looking for, rather than a blind search.
I required all my techs to run all these tests and record the info on the back of the repair order hard copy before teardown began.

Fine, you pull the head and see the headgasket failed at #6 cylinder. Great. But what if #2 cylinder had shown 40% leak down, and the headgasket at that cylinder looks ok? This is where those tests may save you.

 

Is there any reason (I would think not) that I am still holding 13 psi for extended periods of time on a pressure test and maybe Im just smelling the fuel additive, and the second flush round is just freeing up more stuff and creating another blockage?

Wishful thinking but possible haha.

 

How an engine behaves under load, vs sitting in your driveway, is tough to predict.
Run the block test. Pass or fail, you’ve just learned something valuable that will help you narrow your focus. By a lot.
When you flushed the system with chemicals just how bad was the water that came out?

 

I will plan on it. Never done one, assuming I would have to order a test kit or can those be found at auto stores?

It was gnarly. It was a murky brown but no signs of oil (has fresh 10w40 synthetic in the block). I will attach a picture. Just goes to show flushing it a few times wont get it all. I had to flush my 89 five times before I could get the water clear. Truck rarely breaks 185 deg and thats with a probe in the block not the upper hose.

The brown had a slight reddish tinge to it. The thought crossed my mind that maybe a previous owner mixed coolant colors. Havent seen any evidence otherwise including when i cleaned out the overflow tank.

 

Many of the chain parts stores offer both the block tester and leak down tester in their tool loaner programs. I’m guessing you’ll have to buy the fluid.
Block testing is pretty easy, but they’re are a few things you need to do. Drop the water level a bit so you don’t suck liquid into the vial. Only vapor is supposed to pass through the chambers. Get the engine hot enough that you have circulation at the radiator, then you can put the tester in the radiator neck. If there’s an internal leak you should see the fluid go from blue to yellow after 3-4 pumps.

I wonder if draining and filling with a vinegar/water mix, circulating, then letting it sit overnight would help. Vinegar is amazing on scale and hard water build up. If you try, make sure to neutralize with baking soda afterwards.