Swapped the thermostat for a AutoZone Duralast (I didn't even spill any fluid this time, yay me!) and started the truck up. In 5 minutes, at only 70 degrees today, I was back to 230, 240, and creeping home...Radiator was the only thing I hadn't replaced in all this work... The thing is, no weird colors in coolant, when I filled the entire system, I used exactly the proper amount, etc. None of the usual signs of issues...

 

I would still suggest you try Extinct's suggestion of running it with no thermostat at all but I suspect the problem is likely a little deeper.
Radiators don't usually plug up quickly so I'm not sure that is the problem either.
Try to determine if the the pump is circulating coolant. It wouldn't be the first time a water pump impeller failed.
I'd also check the inside of that kinked hose to see if the lining has possibly folded over blocking the flow.

 

Checked the thermostats in a pot of boiling water and they open close normally. Pulled the serpentine belt and the water pump turns nice and smooth. Checked inside the hose and liner and everything is nice and clear and only 3 months old.

Any other items to check before radiator replacement? Looking at the Nissen radiator and Delphi temp sender from Rockauto (best pricing) - anything else to replace/check in doing this swap?

I hate spilling coolant more than anything else...

 

@Discoidiot Check you hoses are they hard, I am assuming you are not losing coolant. I would start with a new rad they are cheap enough and you get that out of the loop.

 

Thanks Richard - yes, back in January I replaced the entire cooling system - new hoses, water pump, cam sensor, reservoir, etc. Radiator was the only thing I didn't touch.

 

Swapped radiator and was so proud for not making any kind of mess.

Unfortunately, temperature is still climbing and nothing seems to have changed.

Any other diagnosis suggestions?

 

Are you losing coolant? How is compression?

 

No loss of coolant, compression is my next check. Valve cover leaks, not horribly, but was going to be part of this summer's maintenance. Water pump was replaced 2 months ago, wouldn't think impeller would fail that quickly and I don't hear any bearing issue when I spin it freely.

 

I went through this in the summer of 2023. That is how I discovered this thread. I had no coolant loss, new water pump, hoses, thermostat ( inline), and new radiator. It turned out to be a cracked block.

 

That's my fear...