We are throwing a lot at you I’m sure. But here’s a little more.
First thing: after your trucks cooled off and it’s next day what are your temps.
Oil & Cooler ?? are they both the same temp before starting?? 1-2* difference tops.
If trucks not run 12 hours or so is temps same as ambient temp ?
25* is horrible and will raise hell and needs to be addressed.
Coolant type ? CAT EC-1 type is by far the best.
Thermostat age & make. Motorcraft 194* is go to.
Oil cooler ? Motorcraft again go to.
I’m against pouring in a acid period. Acids on iron flashes the metal ( burns away outer layer) and it’s microscopic and since iron is porous it goes in a ways. The acid stays reactive until it’s ph level is dropped by a soap or recommended fluid for the cause.
What happens much too often is the flush to remove the acid doesn’t remove all of it due to all the casting flow areas. So the acid left in the pores of the iron keeps doing what acids do: EATING away at the casting. It falls away taking the casting sand from the forging process with it.
The metal and casting sand catch a ride in the coolant and get busy plugging up the new oil cooler just installed 2 weeks to 2 months after the acid flush was done.
I say DONT DO IT.
There are no kidding thousands of Threads: New oil cooler plugged 30* 2 weeks after installed in one form or another.
If your system has oil in the coolant use Simple Green first to break it down. Then go with liquid Cascade w/Dawn Dishwasher soap.
The stuff works and it works well. Been used in shops when I was 15. That’s 40 years ago its not a new hair brained idea. Look at your glass cups after a cycle. It’s a inert cleaning agent that is anti suds and doesn’t bind to water or solids. It leaves nothing behind ( inert). Gods gift.
Then you need to look at how to back flush your oil cooler. If the cooler is a off brand like John Galt stated there’s NO.CURE replace it. Motorcraft or get the hatchet. Sinister is crap too if someone tells you different, smile and never listen to them about squat for the truck.
Flushing these engines ain’t no picnic. Lots of u-tube clips on proper steps.
I will give it to you brief. LMAO here comes brief
Pull BOTH BLOCK PLUGS.
Pull off lower hose at radiator.
Pull thermostat out
Pull coolant tank out.
Separate two hoses to the tee.
Take oil cooler cover off and get 3/4” clear hose for connecting to port.
Take hose #1 Wrap a towel around it and force up lower hose you pulled off radiator
Take hose #2 and force water through hoses that you separated. One at a time.
There’s a metal line to a hose on pass.valve cover open it too.
Push water through that one like the others.
Clear line to cooler push water in the hose. That forces fluids backwards in the cooler.
Give the engine a good rev every minute or two. This produces high pump flows and blows crap out of the open block plugs. The garbage all sinks to the lower part of the block. But hitched a ride up to oil cooler with time. Got to get the crap out of it. I put a 5 gallon bucket under each block openings water hit buckets. Keep watching those buckets. Once you can’t put any grit in them anymore you have completed the flush.
You will need to fill and drain with distilled water three times. Fill it run 5 mins drain. Repeat twice.
Last step is add 3-1/2 gallons of CONCENTRATE CAT EC-1 along with 3-1/2 gals distilled.
I gotta sleep holy cow. Hope that helps. If you have questions let me know. Oh if God loves you the oil cooler will be 3-5* above engine temp.