It has been warmer here lately and I have been noticing that my truck is running warmer than it did last year. Nothing overheating wise, but the temp gauge has been creeping up more than I ever recall.I know they aren't the most accurate gauge, but my cluster has been rebuilt and isn't some failing 20 y/o stepper motors. Just seemed like something wasn't right. So I replaced the thermostat and water pump thinking maybe something is up. No change. Unfortunately all I could get/had on hadn't was a Motorad Ultrastat and a Gates pump.
Back to the drawing board. Did some looking back and noticed that the radiator I put in it back in Feb 2023, during the motor swap, was a 1" core. Looking up different available options, there is a 1-5/16" core with and without engine oil cooler. So I started thinking... maybe the core is too thin? Maybe the radiator is clogging up? Looking in my coolant bottle, I did see some sediment. Also, my radiator hoses are at least 7-years old and some OE. So I pulled the trigger and refreshed the entire cooling system. A few weeks ago, I went to the junkyard and pulled off of a 2010 Tahoe PPV a 7/9 blade 700w K5L heavy duty cooling fan assembly. So I decided to complement them with everything else a K5L heavy duty cooling vehicle would have.
New Gates hoses on everything, new heater hoses, new GM spring clamps (looked up a 2020 Savanah van and bough all the clamps listed for that)... got rid of the worm drive clamps on some things. New GM water pump, new GM thermostat, new coolant bottle, new Denso 1-5/16" core radiator (with engine oil cooler). I figured, if I am putting a radiator in it, it would be cool to have oil cooler lines. So I bought GM oil cooler lines for a Escalade -- wasn't too bad to do once you pull the front driveshaft and lower the front diff a few inches. Used a M8 flange bolt to bolt the line holder to the boss on the block. Even bought the $4 plastic line holder to secure the cooler lines to the back of the fan assembly. Replaced the AC tensioner as that was weak,
Flushed the block and heater core with the garden hose, blew both out as much as I could with the air hose. Filled up with Dexcool concentrate + distilled water aand drove it around a bit. Temps stay excellent. Then again today I drained the radiator and filled with fresh coolant just to cycle through any of the tap water I had in there. I'm not terribly concerned. I may do another drain and fill in a few weeks
Man am I beat, but pleased with the results. Might sound dumb but I am happy to have the additional oil cooling and happy with how cool it is staying. I love how it looks completely factory with the plastic clip and everything. Amazing. Will help when we travel/tow the trailers.
Additionally, with looking at the old radiator, 1/2 of it was gummed up with oily dirt/sediment on the exterior. Shortly after installing that rad (Feb 2023) had a power steering line come off and it sprayed oil everywhere. Perhaps this was also a contributing factor to its decreased efficiency.
One last thing, when I was under the truck, I found a ground that was repaired by a previous mechanic with a horrible crimp ring terminal. Was green and crusty and something that would completely cheeze-me-off when it fails in the middle of winter. Cut it back to clean, new crimp and seal weatherproof ring terminal and a liberal coating of Fluid Film. Glad to have found that.
The old 3.9L sure is making a lot of bottom end noise for 102k. 
