Hey everyone , My 2004 f 150 heritage 4.6 l the oil pressure dropped all the way down i was in a drive thru and it was clattering really bad so i pulled into the parking lot and shut it down pulled the stick plenty of oil i re started about 30 minutes later and it pumped oil pressure. so i started on my way home the guage would go to normal and when i would touch the brakes and let off the gas it would drop and the oil light would come on and the engine would start rattling and would have no power i would pull over and doit over again and finally i just called a tow truck. so i changed the oil new motorcraft
filter and 5/30 motor oil , it started up made all kind of noise but i got oil pressure and quieted down i went to drive it and as soon as it started to roll
the pressure dropped and the oil light came on and it started to rattle again.
whats happening is the pump going out ? can it be replaced with out pulling the engine? any help would be helpful the truck has 200,000 miles on it

 

Sounds like a restriction in the oil pickup area. It also could be a worn-out oil pump or even coked-up block/heads that are not letting the oil drain back. I believe it actually is an oil-starvation problem because you have the symptoms of it, rather than simply a bad gauge. Additionally, it is possible that it is related to the use of certain oil filters that tend to break down and allow papery materials into the system. The Motorcraft filter does not seem to break down this way (as far as I know) but of course its unknown what filters may have been used on it in the past.
So you have some things to check for. Others with experience with the late-model Ford V8s may have some thoughts concerning low oil pressure to the cam assemblies in the heads which is probably where the clattering originates. You'll be lucky if you can restore oil pressure with no permanent damage in the bottom end or cam areas.
I think you will have to pull the oil pan and at least one cam cover to look for sludge deposits, both hard and soft. Since this will be expensive work, I most likely, if it were mine, would first use a solvent in the oil meant for this purpose just to see if it makes any difference. The most aggressive of these is Kreen by Kano Labs, the makers of Kroil. The least aggressive would be Marvel Mystery Oil or Seafoam. Its probably a good idea to start with a mild solvent first, which may be enough. The mild ones are not meant to be used and drained, rather, they work over time and are left in and refreshed in-between oil changes. Kreen, in 8 oz. doses, is also left in, but in the larger doses is meant to be flushed after a short, easy drive. You'll see why when you drain the black oil.
Anyway, I think I've had too much coffee today and am rattling-on, so to sum up, most any mechanic is going to say first you have to identify the problem by looking before any 'snake-oil' doctoring. He also will probably say to replace or overhaul the engine if he finds hard sludge blocking the oil pump pickup screen, which usually will indicate that condition in the heads too.

 

well i put sea foam in it and ran a little while it was holding oil pressure
but the valve noise from the front of the engine was crazy, so i dumped the oil put a new filter and new oil started the truck up and actually i drove it around the block , the oil preasure maintained its self , so my next step was this I tore down the front of the engine removed the timing cover and found the chain guide was broken and dislodged the chain on the driverside was grinding it up .
so my next step i think is to pull the pan , the engine inside is clean no sludge.
and remove any forien material i.e ground chain guide out of the engine that explains the engine not performing very well i am lucky i didnt jump time , next question should i replace the oil pump???

 

Depends on what you find. I would be willing to bet the holes in the oil pump pickup are clogged. If not, replace the pump with a high capacity pump.

 

What kind of oil filter do you use? Cheap aftermarket filters(Fram) can break apart inside and small bits of the glue gets trapped in the oil orifice in the cam caps. That will cut off oil the that head and will starve the tensioner. The orifice is in the last cam cap on the passenger side and the first one on the driver's side.