Always that Chance...
Some Suggestions for Follow Up Diagnostics:
(1) Avoid running the Motor...
PERIOD.
(2) Drain the Engine Oil... Pull the Oil Filter and perform an Oil Filter Autopsy
with a Magnet.***
(3) Look into the Oil Drain Pan for any signs of Water-Coolant in Quantity & Floating Alum Flakes.
(4) Turn the Engine over via the Crankshaft Bolt
(in a CW Direction Only) to TDC on Cylinder #4.
(5) Pull the #4 COP & Spark Plug and Poke a 7-9mm Fiber-Optic Bore-Scope down inside.
(6) Any Bright and Shiny Clean Piston Top Areas will reverse vector to the Head Gasket Leak.
(7) THIS Observation proves a Head Gasket Leak and a HOT Coolant Spray onto the Piston.
(8) Open the Radiator Cap when Ice Cold and look for Oil Droplets Floating on the Coolant.
(9) Open the Coolant Reservoir and look for Oil Droplets floating on the Coolant.
(10) Look underneath the Vehicle for signs of a Con-Rod Cracking-Thrown THRU the Block.
Consider that if the Piston Top in the #4 Cylinder is
Scoured CLEAN that either the Engine has Over-Heated and the Aluminum Engine Head Warped... or that the Water Pump and Coolant Thermostat failed and the engine was run
HOT.
Ordinarily... with the Head Gasket being of an MLS Design of Multi-Layered-Steel
(Coated in a Ceramic Like Paste when Brand New around the Upper Rims of the MLS Cylinder Holes)... it will be very unlikely that IT failed from any Hot Gas Erosion. Broken Head Bolts may cause damage from a Turbo-Charged or Super-Charged System causing Detonation. NON-NA (Natural Aspiration) style Intakes will tend to suffer in this way.
Another possibility is having a Melted Through Piston Top caused by Very High Secondary Voltage coming from a durable COP Electrically Arcing High Voltage into the #4 Aluminum Cast Piston or around the Valve Seat(s).
Lastly... if NO Oil is found in the Coolant and the #4 Piston Top is still covered in Black Carbon ... a Broken Rocker Arm in the #4 Intake and Exhaust Valve location(s) of the Valve Train might be involved as this HAS happened on several prior occasions.
Pulling the Valve Cover allows for total access to the Valve Train to investigate this possibility. The very last possibility is either a Burned Exhaust Valve, Bent Valve Stem... or a Loosened Valve Seat which HAS happened on some of the early Model GMT360 2002-2004 Engine Heads.
*** How To Perform an Oil Filter Autopsy
We have been having a fairly steady increase in the number of Engine Problems with the GM Atlas LL8 Motors that all eventually leave the Member Owners wondering about whether the problems involve the Lubrication System and prompt the Head Scratching Question of “I wonder what the Hell is Really...
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