Many times there is not warning with this engine design incorporating a water pump internal to the block until it's too late. Why, because it can be a slow leak of antifreeze, which contains glycol, into the oil which can cause severe problems. It took about one minute to find an article on the topic of antifreeze/coolant/glycol mixing with oil in an engine:
"Few things are more damaging to an engine than coolant mixing with the oil. Coolant can enter the oil by many avenues and is very hard to find, until it is too late.
Ask most enthusiasts how to identify water in their oil and the most common response is a brown-milky appearance. Enough water in motor oil may turn it brown and milky. More often this is NOT SO with coolant in today’s oil. Modern oils contain detergent and dispersants and great damage may be done, before we notice any outward appearance.
Moisture in normal operation
All engine oil is contaminated with trace amounts of water in normal operation. The heat and cool cycles allow moisture to form in the crankcase. Detergent and additives in the engine oil, pick this up and hold it in suspension, helping to prevent a sludge build up. When the oil temperature reaches 212 degrees Fahrenheit, the water boils and turns to steam. The positive crankcase ventilation or PCV system draws the moisture out and helps prevent problems. With vehicles not driven far enough to reach full temperature, this may not occur. This is why driving only short trips requires more frequent oil changes.
Problems with coolant in the oil
Engine coolant is a combination of some form of glycol and water. Glycol presents several problems when mixed with engine oil. First is, it does not boil away, like water. Instead, it forms organic acids, thickens the oil and reduces its dispersancy. Depleted oil no longer contains the soot from combustion and sludge soon develops. Acid attacks the metal components in the engine producing corrosion and debris.
Increased viscosity does not flow properly, reducing lubrication and the oil filter plugs up. Engineers design oil filters to bypass when anything restricts them. A bypassing oil filter allows debris to flow through and engine failure is not far behind.
Recognizing the symptoms of glycol in engine oil
An early warning is the loss of engine coolant. They seal all modern cooling systems and losing coolant is NOT normal. When the coolant level drops, a problem exists and quickly finding the cause helps prevent more damage."
I speculate that the 3.5 duratec engine was put into the Explorer mainly for gas mileage standards and competition from SUV competitors there able to get more miles per gallon, and as mentioned partially due to engine compartment constraints. With that said, they had no problem in previous generations with fitting 4.0 and 5.0 engines, but gas mileage was less. I realize this is a new body design, but I believe they could have easily tweaked it to fit the engine in from front to rear, not that difficult. I also think gas mileage drove Ford to utilize a unibody design with lots of aluminum used through the vehicle.
Having the water pump inside the engine block is a very poor design IMO, especially with negligible mention of maintenance mentioned in the maintenance manual up to 150,000 miles. When an external water pumps fail, more times than not it's easy to detect with absolutely no danger to engine from glycol mixing with oil and they are easily replaced for reasonable price. Failure of both external and internal water pumps can cause the engine to overheat, but again, the real danger of the internal water pump is slow leak of antifreeze into the oil. It should be noted as mentioned above that the cooling system is a close system where the vehicle owner should only see negligible losses of antifreeze over time.
The current generation of Explorers is still fairly young, but I anticipate that this issue will only grow over time because many people that have owned Explorers in the past are accustom to owning them with low to moderate maintenance costs over lots of time and miles. Because the popularity of this current Explorer generation, Ford will generate lots of revenue replacing both water pumps and engines IMO. It will probably hit the 2nd and 3rd owners of an Explorer vs the initial buyer or owner.
I've mentioned many potential options that I believe Ford should look into from some sort of cost tiered approach for replacing this $40 part as well as putting out a TSB that would retrofit some sort of sensor in the plastic coolant tank so that the owner would know they are losing too much coolant too quickly. Perhaps another idea would be for Ford to put out a TSB with some sort of sensor that could detect glycol in the engine oil so that it is caught before catastrophic damage to the engine.
