Just realized my fan theory is improbable. Guess I’ll just have to put everything back together and see.
They did make a change on the pumps and t-stats. New part for the t-stat only is sized differently than original. When we have a t-stat issue on an earlier truck we sell the pump and t-stat together.
My 5.3 typically is a pain to fill and not get a air lock. If you have a vac-n-fill tool you'll avoid the problem. Most tool trucks sell them. My guys have snapon versions. It uses shop air pressure to draw a vacuum on the system. Helpful to see if it's sealed up, it will pull a vacuum, not sealed it won't. You'll know before putting coolant in it.
If you don't have access to one, pull the upper hose and fill from it. Burp while running. Should come out.

[whispers] biig blooock [whispers]![]()
Never checked. Gm has a special tool very similar so I end up borrowing from work. They might have though. Cool thing is once you shut the air off and open the valve for the coolant it just sucks it in. Pretty darn slick.I know the quality is different but I wonder if this might be something available in a parts house rental tool program?
One thing I noticed in your last post on the fans. You say you can turn on the high temp fan on with HPtuners right? To me that confirms your circuit for the high fan. If the wiring was the issue you wouldn't be able to do that.
Yeah I had that thought too. That would mean we didn’t do something right when he came and set the temps. I really don’t want to have to pay another $150 for that
I don’t have experience with any other square body than my own, but I’ll give you my experience.
My 6.0L with a griffin and a Taurus two speed fan will run all day with out turning on the second speed. I’m using the Volvo relays for the two speed. I’m set at 194 for first stage and 201 for second. Stop and go with the A/C on and 95F in the sun and I’ll hear the hi speed off and on. I’ve had the coolant drained down to the temp
sensor level in the block and had no issues bleeding the system.
I don’t have the hopped up cam that you do and haven’t personally checked my thermostat for temp.
One way to confirm the circuit without the ecm is putting in a test relay similar to one of these:
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I've got one a tech at work made for me. Take a spare relay and pop the lid off of it. Disable the load side of the relay and connect those two terminals to a manual switch with a couple of wires. Plug the relay in and you can override the ecm and force the fan on. Again, it confirms the circuit but only from the relay to the fan at that point. You could do the same thing with a power probe too if you had one.
You could confirm the control side of the circuit from the relay back to the ecm by checking continuity on it with both sides unplugged. If you have continuity and the fan works with the relay, the ecm isn't commanding the relay on.
Continuity is checked with the circuit disabled. As in unplugged at the relay and the ecm. Using the ohmmeter of your meter you connect your leads to the relay terminal for the control side and the pin at the ecm connector for the high speed fan. Still, if you commanded it on with the tuner software to me that proved the circuit was ok.
I'm a complete noob to tuning, but the screenshot raises some questions. Besides the temp values being on the low side, the ac enable/disable pids don't make sense. Enable and disable are set at 500psi. Is that just to not have it looking at ac pressure since you don't have a/c or at least a pressure sensor in the a/c system? Also the on temp a/c on for fan 1 is set to 284* which might be in someway dictating the fan #2 is not coming on even though the listing was for fan #1. Also the enable speed for fan 1 is 250 mph. Huh? Is that to mean the truck has to be moving 250 to enable the fan? Sum Ting Wong.
Like I said I'm no expert on the tuning side of things, but some of those settings seem odd to me.