In the last month, I've noticed my oil pressure dropping at idle when the engine's at normal operating temperature. I'm hoping someone can help with some advice on what might be causing it. Sorry for the long post, but I want to describe the problem and list what I've done in hopes that it will help with a diagnosis.

The engine has not been overheated or abused in any way. The HPOP is probably original and has about 223K on it. Same for the engine oil pump.

At idle, the OP indicator starts to fall off and gets erratic, sometimes going all the way to zero, but usually flipping around between normal and zero.

I installed a mechanical gage to get quantitative readings. The oil pressure goes to 5-6 psi at warm idle (~600 rpm per the tach), which is pretty close to the trigger point for the OP sending unit and explains why the gage is erratic. I connected the mechanical gage to the port on the oil filter head. I also replaced the OP sending unit with a new one from Ford, but got exactly the same readings.

Bumping the throttle just a little causes the dashboard gage to recover to a normal reading. Oil pressure at idle with engine cold is 20-25 psi. Oil pressure with engine at normal operating temperature at 2000 rpm is ~50 psi.

I ran synthetic Rotella 5W40 through the winter, and just changed back to regular Rotella 15W40. All pressure readings above are with the Rotella 15W40 oil and oil level on the full mark.

The injectors were changed out last December, but no unusual smoking or oil consumption since then.

I gutted the EBPV and actuator, and replaced the pedestal o-rings about 2 weeks ago, but was seeing the low pressure at idle before that.

Nothing unusual in the fuel filter - it was changed at the same time I changed the oil.

I haven't noticed any new knocks or unusual sounds at all. The truck runs great.

There is an external oil leak that appears to be in the oil pan seal, just below the crank shaft at the rear of the engine. I removed the TC inspection plate to confirm that the oil is not coming from the rear main seal. With the engine at high idle (~1100 rpm), the oil drips off the lip of the oil pan just below the crank shaft. There are no oil leaks on top of the engine - the valley is dry. I've checked the plugs at the back of the engine by feeling for oil (I haven't tried getting a wrench on them to tighten them). I'm losing about a quart per 200+ miles.

My fear is that there is some kind of internal damage, maybe from using the light oil, or maybe using the synthetic did something. Can a worn out HPOP cause this? Or a worn out oil pump? I'm running out of "easy" stuff to check. Any ideas would be appreciated.

 

probably the oil pressure gauge. best way to be for sure is to hook up an aftermarket to the hpop res or down by the oil filter.

 

Did that - oil pressure drops to 5-6 psi at idle when warm. Thanks

 

UGH, I hate low oil pressure problems. It's always a mechanical failure somewhere.
I've never been inside a PSD to offer any personal experience.
I've read on several occations of the piston cooling jets falling out of thier sockets and dropping into the oil pan. That would open up a big port for the oil to bleed off and drop your pressure. I suggest finding a shop that has a borescope. Authorize an oil change so they can remove the drain plug, let the oil drain and insert the borescope through the drain hole and inspect the jets.
I've also read about the LPOP simply wearing out.

 

Thanks for the response, Kwik - looking like some major surgery may be needed. Since the engine has to be pulled to fix the oil pan leak, hopefully whatever's causing this oil pressure problem can be corrected without much more pain.

I've read that the LPOP can be replaced fairly easily without pulling the engine. But wouldn't a weak LPOP cause low oil pressure at any engine speed? I'm assuming the 50 psi @ 2000 rpm that I'm seeing is normal.

The cooling jets sound like a good possibility. Can they be replaced from the bottom of the engine without tearing anything else apart?

If anyone else has suggestions, please post them. If nothing else, I'd like to go to a mechanic with at least a half-@xz idea of what to tell him.

Thanks,

 

i think you can drain oil and tap on oil pan to hear if you got em rattling around.

 

i am sorry i didnt read your whole post the first time. my time is limited on here these days.

i have read about a pick up tube leak problem before but dont know if these symptoms are what you have or not. let me try and locate it. and ill get back to you. i have also heard of what kwik said but have no idea of those symptoms either.

 

If you have the engine out, it's a perfect opportunity to get it done right. I'm spending your money here, but if it were my truck I would be buying a new oil pump regardless if it's good or not. At the very least, replace the gaskets for the pickup tube. Also I would check every hold down for the cooling jets to make sure they are tight. If all seems to be in order I would pull a bearing cap or two and see what's up.
I don't know if the possibility exists, is there an overflow valve for the HPOP reservoir that maybe is dumping pressure there? Or an o-ring for the HPOP supply that might have failed?

 

try this to elimnate the oil pickup tube being cracked. found it at identfix while trying to figure another problem on a customers vehicle.

Cracked Oil Pump pickup tube, leaking pickup tube seal at timing cover, faulty engine oil pump or worn crankshaft bearings resulting in low engine oil pressure.


Test & Fix:Crank the engine while monitoring the engine oil gauge on the dash. It should jump to the mid range within 5 seconds of cranking. It will read there with as little as 5 PSI oil pressure. You can also verify oil pressure by installing a master oil gauge in the top of the ICP reservoir in place of the oil pressure sender. If either gauge fails to register and the engine crankcase is full, overfill with 3 additional quarts of oil and raise rear of vehicle approximately 10 inches. This will fully submerge the pickup tube and its seal at the timing cover. If the oil gauge now responds correctly while cranking and the engine starts, the problem is likely due to sucking air caused by a cracked oil pickup tube or leaking seal. If there is no change in operation, the problem will likely be either a defective engine oil pump or crankshaft bearing concern. Disassemble and repair the engine as needed.

 

tjbeggs - thanks, this is good stuff. I'll give this a shot asap. Hopefully, if it's the LPOP or pickup tube/seals, it can be repaired without pulling the engine. Thanks again!

 

Thanks - excellent advice. I want to avoid pulling the engine right now, if possible, and just live with the leaky oil pan until I can stand to be without the truck. The oil pressure problem needs attention quickly, though. I was wondering about the HPOP, too. I know the LPOP feeds it, but I'm not sure whether that feed is regulated somehow, and if so, if the regulation goes out in some way, whether it would bleed oil pressure.

Does anyone know?

 

I know this is an old thread but... did you ever figure out what was causing your problem? I am having the same issue with my truck right now.