Hi,
Pretty Nasty! The mystery sludge in your coolant passages is inorganic salt, separated and solidified from & within coolant, & possibly “hard” H20. Occurs in non-coolant changed Motors. Coolant containing inorganic salts, nitrites, phosphates and silicates.
Excess minerals accelerate the process. “Hard” water, an example.
High Silicate #’s cost less than running Ethylene Glycol, it lowers boiling points similar, & low temperature protection similar to Ethylene Glycol based Coolant. Cheaper.
Inorganic salts deplete within a couple years. Once depleted, they become slimy, pasty, cause restrictions, blockages.
Like feeding yourself a giant 3lb Triple bacon cheeseburger if you have Heart problems.
Did you try bypassing the heater core? Still together, garden hose,.
The CPU CTS will give false readings if any crud or air cavities exist, same W/Gauge.
Isolate the Cylinder that runs hottest in the Head. Yank each Cyl’s wire, 1, try, replace, 2,try,replace, etc. Bubbles in Coolant concern, should be less, none at all if a leaking Cylinder’s Combustion stops.
No PCV. Blocked off, or in place, disconnected? Plug connected to a bypass?
A chunk of debris may have broken loose & travelled when the Coolant line burst, flow altered, blocking a coolant passage..
The head closer in location to the engine’s thermostat housing is less effectively cooled than the other. Passenger side on 5.0’s.
Any possibility the Cat is clogged on that Cyl bank? Verify two plug wires, or injector wires are not inverted..
The salts breakdown, slime to chunky masses, a pasty-like buildup shown in your Pic’s, that’s what’s inside your motor, now, narrow coolant passages most vulnerable.
Smell Coolant at tailpipes? Sweet smell.
Seen this before, only similars that mimic it are adding large amounts of coolant system “stop leak”, barrier at a leak, & wherever else it travels, any coolant lines..
You may be dealing with both..
Since the motor had run very hot, change the Oil/Filter, high temp properties break oil down. Just an FYI, keep in mind...
So, I’d first try these, pull the plugs:
1) Verify whether Head gasket(s) has a Cylinder to Coolant passage leak by performing:
A) Cylinder Compression Check & leakdown tests OK, look in radiator for slow bubbling..
B) A Coolant System Pressure test. Spark Plugs removed from Block. 15psi is fine. Can rent, or borrow.
2) Drain all Coolant from the Block, drop the Radiator hose & dump into a clean bucket. & Measure amount, check Spec’s Exact capacity. Fill the Block with H20, see if the coolant system takes the exact amount
Acquire a Hydrocarbons reader & Check Coolant for Combustion Gases.
Of no findings, or any- post them.
I’ll help you, as will others.
If bubbles in coolant persist, next is Intake, Head gaskets.
A few good coolant flushes.
Pull the Intake off & view the condition of the passages (Borrow/Buy a small tipped Borescopes for best views).
Just Heads up, next.
-If the Intake came from the same motor as the one pictured, Remove the buildup and spray out the passages with compressed air, pull the steam plugs out of the Block & flush it through (Plastic in the valley with rags laid atop, flat). Keep Other clean rags close.. Don’t want any getting into the valley, Oil.
-Run a high-quality coolant using organic-acid technology; “OATs”. This coolant type eliminates inorganic Salt issues due to their composition, eliminating corrosion, formulations May be used in many different app’s, and adding dissimilar coolant types if low(Use after doing tests, pulling Intake & viewing inside crossovers.
Work on that after this-k?
Good luck!
-John