Here is some of the communications going on between Ford and the dealer mechanic:
Mechanic: Once at operating temperature and under load vehicle loses coolant threw degas cap. I checked for codes, no codes, pressure tested, did not lose pressure, test drove under load with pressure gauge tapped into cooling system, highest reading 18psi on test drive, checked for combustion gasses in cooling system and gasses are present, checked egr valve for contamination, none present, no external leaks. Relative compression showed cylinder 2 & 8 down 4%, performed manual compression on passenger side #2 330psi, #4 340psi, #6 340psi, #8 320psi.
Ford: With the presents of combustion in the cooling system, this can be caused by a leaking EGR cooler, a head gasket failure or by a cracked damaged cylinder head. We will first want to test the egr coolers for leaks. We will also want to inspect the egrt sensor on the top of the vertical EGR cooler for a steam cleaned appears. A steam cleaned appearance or liquid coolant in either area would suggest that we have and EGR cooler leak. If no leaks are found, this would indicate that we have a head or a head gasket failure.
However, before continuing with any additional diagnostics for this concern we recommend performing a manual compression test on cylinders 1,3,5 & 7 to get a better understanding as to the state of the base engine. It is best practice to perform a manual compression test on all eight cylinders when a loss in relative compression is noted.
This is recommended because the compression on the left bank is extremely low.If we find a 25psi variation or more between the highest and lowest compression reading all 8 cylinders, this would confirm that we have a base engine concern. In this scenario, the engine will need to be removed for disassembly and inspection to determine the root cause.
Mechanic: checked egrt and even sensor, no steamed appearance found or evidence of coolant. I apologize the first compression reading I sent were for cylinders 1,3,5,& 7, number 2 was 300psi, 4 320psi, 6 340 psi, 8 300psi, removed passenger side head, found evidence or leakage on head gasket, straight edged mating surfaces no concern found, replaced head gasket, performed relative compression, 0% loss in all cylinders, test drove, coolant puking through degas at hard load again, checked relative compression again #2 and #8 down 5%, would removing and inspecting the head again be the next best step?
Ford: If there is coolant punching out of the degas bottle after new head gaskets, and no evidence of coolant in the EGR system, this suggests there is a block concern present. This should be able to be confirmed by draining the oil from the engine, and pressure testing the cooling system. If coolant drips out of the drain plug, then there is a crack in the block, or faulty head gaskets. Since the head gaskets are new, then there is probably a crack in the block. If coolant drips out of the oil pan, then the heads should be removed and the block should be carefully inspected.
If coolant does not drip out from the drain plug, then crank the engine over by hand a little bit at a time. Even until the engine has been rotated a full resolution if needed. Make sure that the cooling system is pressurized the whole time to insure accurate test results. If there is coolant dripping out the hole, then cylinders 2 & 8 should be carefully inspected for faults.
If coolant does not drip out of the oil pan, then carefully inspect the EGR system components for leaks, especially the lower EGR cooler because that's where The coolant tends to collect or be prevalent. It's not suspect that this is the cause of the concern as seen by the compression results. It's suspect that there is a cylinder fault present and that's the reason for the low compression, and the gasses in the coolant.
Side Note: Inspect the charged air cooler (CAC) for oil or other contamination that may be present. Cylinders 2 and 8 are affected the most by oil ingestion from the CAC and tend to be one of the more noticeable cylinders if there was oil ingestion causing cylinder failure. If there is oil in the CAC then the turbos should be inspected for oil leaks
Results: After I discussed this with service advisor, I was informed the above tests were compled for the leakage from the drain plug and oil pan. No leakage of coolant was detected. They are now in the process of checking the lower EGR cooler. Won"t know the results until Monday.
I hope this helps.
