I have a 2003 4.6l f150 164000 miles. While back oil pressure dropped to 0. Then chattering. Then up then down. I changed the oil and filter, then flushed the motor, then changed the oil and filter again. 1500 miles, no problems, no chatter. Then all of a sudden it happens again. Oil level good and clean. Oil pump?? Pick up tube?? Please help. Thx

 

hmm. the oil pressure sending units on these trucks are known to go out, but if your actually hearing chatter, thats an issue. now is it a tick when cold? now there are people on here that know way more than i do but we need more info.

 

Sounds like there is still a sludge issue. Might need to drop the pan and scrape it out, especially around the oil pump pick up.

 

Thx probably cheaper to start with the oil pan than the pump.

 

And there is likely nothing wrong with the pump.

 

You need to put a gage on the port and look at the pressure both cold and hot for any real answer to the issue.
If the motor is sludge's up, it has been abused for oil and filter change intervals.
Good luck.

 

If it is indeed sludged up, and it sounds as if it is, it is highly likely that it has seen it's life doing lots of very short hops. With todays oils, you rarely get sludge if it gets thoroughly warmed up on most of its runs, unless the oil has just been extremely rarely changed.

 

I have the same issue with a 2000 4.6 2 wheel drive. I changed the oil pressure switch and changed the oil thinking that would fix it. The light will come on and the oil pressure gauge will drop to zero after driving for 15 to 20 min. only while idiling. when truck is running down the road the pressure is good.

 

Just because a pressure switch is new doesn't mean it is any good. Best to put a gauge to it and see what you have for pressure.

 

Here is what is normal ranges for oil pressure on 4.6L
The oil pressure 'switch' normally closes on a pressure between 7 to 10 psi.
Since it is a switch it does not show varying pressure on the dash gage.
The dash gauge is useless for anything but the switch is closed or it is not.
Normal cold pressure in a good motor can be as high as 60+ psi.
Normal running pressure hot, at idle, should be at least 20 psi which is more than enough to close the pressure switch.
Running pressure at normal highway speeds should be in the 45 to 50 psi depending on temperature, oil age etc.
If the switch opens at idle, the pressure has either gone down below the switch operate point or the switch is faulty.
If the pressure as measured on a real gauge goes to near zero hot idle, the motor has worn bearings and possibly a worn oil pump.
The oil pump could also have a broken pressure relief spring causing pressure loss to the by pass function.
When oil pressure goes low, the cam timing chains tensioners loose pressure such that the chains can slap causing noise especially if their guides are worn.
Other parts of the motor can go without enough lubrication.
.
Begin with a real pressure gauge to get to the base pressure action and motor condition.
Diagnosing further, If the pressure stays up until the oil heats, it's likely low pressure when the oil viscosity thins from heat.
That should tell you the motor may be in need of lower end rebuild.
.
My 02 4.6 has 210,000 miles with 24 psi hot idle on a real dedicated gauge and runs near 55 psi on the highway at 2000 rpm..
I have been monitoring this pressure behavior for 150,000 miles.
The motor runs as near new.
.
This all supports the use of the proper weight 5w20 and reasonable oil and filter change intervals in the 7 to 10k range over the life of the motor or early failure is inevitable for some areas.
These motors are not the usual push rod design and need more specific attention to lubrications use and change schedules to attain long life they were designed to offer..
A worn motor is to late to start.
Good luck.

 

I appreciate the response, i plan to check the oil pressure as soon as i can find a tester. I don't have one so i am on the hunt, the local auto parts place does not have it.
The operating pressures are just what i was looking for, will keep you posted.