No oil pressure at idle...

[Redneck_Ranger]

Alright, so this has been a persistent issue that I can't seem to figure out... I'll start my truck up cold, and my oil pressure will not come up until it gets warm, 10 minutes later. It sounds like a damn diesel... Valves and lifters rattle horribly. Once I start driving, it drives fine. Oil pressure appears to be where it should be. Once I hit a stop light though pressure drops like a rock. I put 10-40 oil in it, but that only seems to help when it's real cold out... I don't think it's my oil pump, and my pickup tube is clear from debris. I'm leaning toward clogged passages... Any way for me to clear them out without ripping the engine apart? I heard about running trans fluid through for a few minutes....but I was told by professionals not to... Advice, please?

 

[RonD]

Fords doesn't use true oil pressure senders, they are switches so don't give you a true oil "pressure".
Normally I would say replace the sender but.........
The lifter taps(noise) tells you there is a real pressure problem so it is not a sender/gauge issue.

The oil pump pushes a volume out, the resistance/restriction at the bearings create the back pressure in the system, that is what is being measured, back pressure, as an engine gets older the bearings wear and resistance/pressure goes down, but not to 0.
Oil pressure low enough to cause the valve train to make noise means only 2psi or less at idle.
You can remove the sender and put on a real oil pressure gauge to test what is really going on, see what the real pressure is at different RPMs.
Might help diagnose the problem.

Most engine oiling systems pick up the oil in the pan via the oil pump, it then goes to the oil filter, then to the oil passages, the oil sender is just after the filter, that's where the pressure is measured.
If you had a blockage in passages sender pressure would go up because of where it is.
A larger hole(bearing gap) in the system would make pressure go down.

If running a thicker oil helped then it is probably not an oil pump issue, i.e. a volume issue.

If passages were dirty pressure would tend to get higher not lower, restriction is what cause the pressure.
Marvel mystery oil additive is OK to use, but I doubt it would solve this issue, worth a shot.

Regular ATF is a high detergent oil so is OK as well, 1/2 quart is usual, many people add 1/2 quart of ATF after each oil change.
Some put in a quart and run engine a few days and then change the oil.

 

[Redneck_Ranger]

I actually have a quart of Marvel in there now. It did help for a while. So from what you're saying... I could actually add some more oil than is recommended and get away with it?

 

[adsm08]

Putting more oil in it will not help your issue. ATF is thinner than regular motor oil as well, so it def won't help a pressure issue.

I would suspect that you have larger issues and would be putting a mechanical gauge on it really quick.

 

[kimcrwbr1]

About 100 miles before you change the oil add 1/2 quart ATF and put in a cheap filter after about 100 miles drain it good add 1 quart lucas oil stabilizer with 10W40 and a good filter. On my 2.8 I had to do the ATF treatment a few times. It sounds like a oil pump tho how high does the pressure go when driving down the freeway.

 

[Redneck_Ranger]

As soon as I'm on the throttle it seems like it's normal. I threw 3/4 quart of oil into it so I'm running about 5.5 qt of oil and it helped a lot... So I'm going with excessive bearing clearances. That engine is on it's way out... It's been at normal oil level for 6 months and it's pushing oil into the intake, timing chains are wearing out... etc. I don't plan on keeping it for much longer anyways. I just need it running right.

 

[Explorin94]

Like Ron said.....NEVER TRUST THE GAGE IN THE DASH THEY ARE NEVER CORRECT. They are also just a mere switch. Put an oil pressure gae in and see where your actual pressure is.

 

[Redneck_Ranger]

I don't have the time to do that. But it's obvious that I don't have correct pressure when my truck sounds like a diesel at idle..

 

[Fordmastertech]

A lot of the 4.0 SOHC engines will sound like a diesel when cold and have ok oil pressure. Put a real gauge on it and figure out what is going on or just drive it till it blows. If the bearing clearances were too wide it would sound worse when hot.

 

[RonD]

As soon as I'm on the throttle it seems like it's normal. I threw 3/4 quart of oil into it so I'm running about 5.5 qt of oil and it helped a lot... So I'm going with excessive bearing clearances. That engine is on it's way out... It's been at normal oil level for 6 months and it's pushing oil into the intake, timing chains are wearing out... etc. I don't plan on keeping it for much longer anyways. I just need it running right.

If you added more oil then that means the oil in the pan is sitting at a higher level, and then the oil pressure improved.............I would guess a leak(crack or hole), in the pickup tube, if this is true.
Because adding more oil doesn't change the pressure in and of itself, but if the pickup tube is sucking a bit of air with oil at normal levels that would reduce the volume of oil and so the oil pressure would go down, covering up the hole that is allowing air in would increase the pressure.

 

[Redneck_Ranger]

If you added more oil then that means the oil in the pan is sitting at a higher level, and then the oil pressure improved.............I would guess a leak(crack or hole), in the pickup tube, if this is true.
Because adding more oil doesn't change the pressure in and of itself, but if the pickup tube is sucking a bit of air with oil at normal levels that would reduce the volume of oil and so the oil pressure would go down, covering up the hole that is allowing air in would increase the pressure.

That could be possible, I never thought of something like that...

 

[JackDW]

First thing to try, is replace the oil filter. The have bleed back valves and associated items and have been know to cause these types of issues especially cheap filters (especially Fram).

 

[Redneck_Ranger]

I'm using a Purolator filter that's only two weeks old.

 

[Explorin94]

I don't have the time to do that. But it's obvious that I don't have correct pressure when my truck sounds like a diesel at idle..

But yet you have time to sit on the computer and post. If it were my truck I would find the time and get it fixed before you need another engine.

 

[Stangman92]

Could it be rod knock? The reason i ask is my truck sounded like a diesel truck for a week then one night a rod went threw the block. Now it doesnt knock anymore. lol. Good luck