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On 9/14/17, my 1986 F150 was being called upon to drive ~570 miles to Skiatook, OK, for the 2017 OK GTG. It has made this trip 3 times before.
This truck is powered by the 4.9L engine [Duraspark conversion]. The engine has 205K miles and has always run great. My beautiful wife was with me and as we approached Memphis, TN [~100 miles into the trip], the factory oil pressure gauge began to drop. I quickly looked at the fuel and temperature gauges to see if the ICVR was acting up. The temperature gauge was a little lower than normal, but the fuel gauge was about where I would expect it to be. I continued and began to hear tapping. I pulled to the side of the road and listened. The sound was like that of a sticking lifter. I opened the oil fill, with engine idling, and could see oil flowing and the ticking sound stopped. I tried again and as I got up to highway speed [65 mph], the sound returned and worsened. I did a gut check and a small voice told me to head back home. You have to realize that there are parts of Memphis where one does not want to break down with your loving wife of 34 years!
The further I drove [longest 100 miles of my life], the worse it sounded. The oil pressure gauge was steady with the "N" of NORMAL. I checked the oil level and it was full and clean. The higher the RPMs, the lower the oil pressure. I slowed to 50 mph and when going up hills it normally easily "torques" @ that speed, I would have to down shift which caused the RPMs to increase and the oil pressure would bottom out. There were hills [small, normally] where the engine would begin to drop cylinders as the clattering increased. I would nervously keep an eye on the pressure gauge and pray that I soon would crest the hill so a shift to O.D. could be made, lowering the engine speed. By the time I drove into our driveway, the engine was missing and sounded like a number of people were hitting it with small hammers. OUCH!!! I was sick, but the truck got us home before giving up its life [or so I thought].
Unfortunately, our area does not have machine shops which the local reputable mechanics can trust. Consideration was being made into installing a remanufactured long block, but was not necessary, after all. A good friend [local FORD trained Diesel mechanic] agreed to work on the truck and I had it towed to his shop. I did not try to start it after returning from OK [we drove my wife's car] because I did not want to hear it "scream in pain", again. Several days later, my friend said he had started the engine and let it idle for some time and the initial lifter clicking abated after a while. He said it still showed extremely low oil pressure but otherwise sounded good. The oil pan was dropped and the pick-up screen was clogged.
Now, let me provide some history. I purchased this truck about 9 years ago, with ~121K miles, from the elderly original owner. It had never been abused, but had not had regular maintenance. The oil was black with a Fram oil filter and the engine still had the original spark plug wires, radiator hoses, heater hoses, etc. Many vacuum hoses were missing or cracked. The engine bucked and the first 2 tanks of gasoline returned 8 - 11 mpg. When looking into the valve cover after removing the oil fill cap, one could see much sludge on the rockers. I began to reclaim the truck and did numerous "short interval" oil and filter changes using Rotella Diesel rated oil for its high detergent and high Zinc properties. The rockers are now clean and have been for a long time [years]. Earlier this year, when replacing the pushrod inspection cover gasket, I observed that that part of the engine was quite clean. So, in my mind, the engine internals must have been cleaned by the normal oil change intervals with good oil and filter [Motorcraft FL1A]. Apparently, WRONG!
Just before the tow truck arrived, I checked the oil level, which had just been changed before the trip and was on the "calibrated by me" oil mark. It now was ~1/2 quart above the line???
A close inspection of the fuel pump looks like it has just begun to leak internally to the crankcase.
The bottom of the oil pan had more crud than I would like to have seen. I am theorizing that sludge as seen on internal engine parts must have some "carbonized" part that does not dissolve with the detergents in the oil and just settles to the bottom of the pan and not flow out with hot oil changes. Anyway, the screen is covered with a metal baffle and maybe a 1/4 - 1/3 open area with no baffle. Looking under the baffle, it was full of black crud and there was some blockage of the non-covered screen.
Maybe the leaking gasoline thinned the oil and introduced unwanted solvents which loosened the pan bottom crud. As engine speed increased [I normally go put-put; ask Gary], the loosened and softened sludge was sucked up and blocked the only open area of the oil pick-up screen, thereby blocking the oil flow?
The oil pump has been replaced along with a new pick-up screen and tubing. The fuel pump has been replaced as well. While the pan was off, the raised areas which encircle the securing bolts, locating the original cork gasket, were ground smooth. This is a neat trick which enables one to install the 1 piece oil gasket, which Ford used on the later 4.9L engines, updating the 4 piece [leak prone] original.
6 quarts of 10W30 and a new FL1A oil filter and the engine sounds great and the oil pressure is back to normal.
I will change the oil again in about 300 - 500 miles and have to regain my confidence by taking longer and faster trips, but as of the 24 hours I have had it back, all is well.
Sorry for the very long post, but maybe this will help someone else.
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