Guys (and Gals) need some serious help here! I have a 1999 Superduty F250 4X4 Regular Cab / Longbed XL with the 5.4L gas V8. At 89,000 miles, the engine spun a rod bearing and as soon as I heard the knock, I shut the engine down immediately. I had the problem diagnosed and the engine rebuilt by someone who came highly recommended and although was not a Ford authorized mechanic, had done many 4.6L rebuilds. He said the cause of such an early failure was apparently due to the fact the previous owner did not complete scheduled oil changes and the oil intake was severely blocked. To make a long story short, the mechanic completed the rebuild which included new rod and main bearings, rebuilt rods and crank, and a new oil pump. About 50 miles after getting the truck back, I noticed that once the truck warmed up to operating temperature, the oil pressure needle would start to twitch and then drop to zero completely whenever the truck came to a stop and was idling at about (750 rpm's). As soon as I'd give it a little gas and get the rpm's up to 1000 or more, the pressure would pick right back up. After putting in a new oil pressure sending unit and seeing no change the mechanic took back the truck and took the engine back out. What he found was that there were no cracks or blockages of the oil intake tube and that the rod bearings were getting enough lubrication but that the main bearings were not. The problem is that the mechanic isn't certain what's causing the problem. He suspects that he may have missed a blocked oil passage but after having the truck now for three weeks, does not have a definite solution. Any ideas that you have that I could pass on to him would be greatly appreciated. In total the truck's been down now for 7 months as I had to save the money for the rebuild so as you can imagine, I'm somewhat desperate to get if fixed quickly but most importanly, to get it fixed right. Thanks in advance for any constructive advice.
Kevin

 

It sounds to me like its got a leak not a blockage. My guess is the block has a problem and the engine is losing oil somewhere Or its got a oil pump intake problem.
Whats happening is the engine doesn't have enough oil volume to keep the pressure up. I'm thinking thats why the original engine failed and the mech didn't pick it up. Every oil passage needs to be verified. Very time consuming but it has to be done. One other thing the oil pressure bypass needs to be looked at also. You could have a problem in a head casting or block casting..


Hope you find the problem. Welcome to the site.

 

One of the issues with these engines is not using the recommended 5W20 oil. Thicker oils, such as 30W, often won't work properly in the 5.4 Triton engine or its kin--possibly due to the nature of the oil pump. The engine has been known to spin the rods on the 4and 8 pistons--even with an adequate oil level on the dip stick--but by using the wrong oil in the engine. I have read posts on this site where this issue has damaged several engines' crankshafts. It is an expensive and time-consuming repair. The rods and the rod caps have to be mated with each other exactly as they were set when the engine was taken apart. The main bearing caps are numbered and a good machanic should have install them correctly. The mechanic could have put the halves with the oil holes in them upside down, but that isn't likely--if he is competent. Good luck.

 

99 5.4 takes 5W30 not 5W20..At least thats what it says on my oil cap. They changed it in the latter years. This is an old thread!!


Dick