Drastic drops/returns of oil pressure (5.4L 3v 2009)

[TnFordDad]

Background: I have a 5.4L 3-valve manufactured in 2009, with 195,000 miles. (Probably not relevant, the cam phasers were locked out a few years ago.) My wife was in a wreck (body damage only), so the vehicle sat for a couple of months until insuranced and body shop got it looking good again. Upon picking it up, though, I discovered a new intermittent oil pressure issue. The motor oil level is at 100% capacity. For the last 6 years, at least, the motor has had full synthetic 5W20 oil changes every 3k-5k miles.

Sudden oil pressure changes: Upon starting the motor, it runs just fine (at least while sitting on the level), with the oil pressure guage staying above 50%. I have driven it as far as 5 miles / 10+ minutes, and at speeds up to 45 mph / moderate RPMs, and as long as the road was essentially level or facing downhill, the oil pressure guage stayed a well above the half-way mark (maybe 60-65%). However, fairly soon after starting up notable incline, the oil guage freefalls and bottoms out; the oil light/alarm activates; and I start hearing valve/timing noise. If I stop it at the top of the hill incline, turn everything off, let it sit for a 1 minute, and restart, oil pressure comes right back up to normal. So, it's not a sending unit issue, there really is a drastic loss of pressure, but it will disappear as quickly as it starts. But there is no middle ground of having low pressure--it's either plenty high/good ("on"), or catastrophically low ("off") (yes, I know a crankshaft driven oil pump cannot "turn off," but the difference is so drastic as look like somebody did switch it off or on.)

Motor condition/damage status: I have been careful not to drive it at any high speeds/RPMs, drive it more than 1 minute or so with low pressure, or let it get hot. It's been driven approximately 12-15 miles total since first instance, plus 2 different mechanics idling it to see/hear problem. At this point, the engine sounds great until oil pressure drops and as soon as it returns. So if I need to drop $2k+ on an oil pump / timing component overhaul on a motor with 200k miles, I would rather spend $5k - $8k on a motor replacement. BUT, I am hopeful that the motor will still last a while if there is a cheaper fix for the oil pressure problem.

Questions: 3 shops have advised me to just replace the motor. I have some thoughts about diagnosis and repairs vs. replacement, but I want to see if others can suggest ideas I have not considered.

1. Ignoring for a moment the incline/uphill variable, what are any/all conditions or malfunctions could cause a sudden, drastic--but not permanent--loss of oil pressure?
2. Factoring in that slope/incline seems to have a direct effect on whether oil pressure is "on" or "off," what are your potential diagnoses / possibilities?
3. How likely are the bearings, timing components, etc. to have been damaged enough to kill the motor in the near term?
4. Any other thoughts, suggestions, or advice?

Thank you!

 

[Brons2]

That's a tough one. Maybe the 2 months sitting was enough to dry up the o-ring between the pickup tube and the oil pump, and at certain angles, it's sucking air. Or the impact, however cosmetic it might have been, has damaged the pickup tube.

You said you've locked out the phasers, if you've never replaced the chain tensioners, you should do that also. They have very small o-rings that seal them off from the block and they frequently blow out.

I would replace the oil pump, pickup tube, o-ring and tensioners before springing for a new engine. Melling makes a high volume oil pump for these, I have one in the garage to go on mine.

It's time for a timing job at 195,000 miles no matter what. Once you have all the timing components off, the oil pump is right there. If you're not DIYing and plan to keep it for a few more years, a new motor may make more sense for you. For me it would not make sense because I will be DIYing and my all in cost of replacing everything that the chain touches plus the oil pump and gaskets is less than $1000. But it costs a lot to have someone else do it for you.

 

[TnFordDad]

I would replace the oil pump, pickup tube, o-ring and tensioners before springing for a new engine. Melling makes a high volume oil pump ...

It's time for a timing job at 195,000 miles no matter what. ... If you're not DIYing and plan to keep it for a few more years, a new motor may make more sense for you. ... it costs a lot to have someone else do it for you.

Yes, unfortunately it's not a job I would be doing myself. I have completely rebuilt motors when I was younger and had the time, but I rarely have more than a couple hours free in the evening in any given week, and weekends are rarely free, either. This is my wife's daily driver, leaving us with only one vehicle for getting me and her to work and 4 kids to 3 different schools, plus our oldest's place of work. If I DIY'd it (which would be fun), it might take me a month or more to get it all done and back on the road. If this was a spare vehicle, I think I would give it a shot and teach my boys the stuff that so few kids ever learn these days.

Thanks for the suggestions!

 

[bodabdan]

Pretty sure your factory oil pressure gauge is just actually a switch. I think it's 7? psi switch, good gauge reading only means more than 7. Maybe 10, maybe 60. It's more like an idiot light than a gauge.
With the mileage on it and having oil pressure issues, you probably would be better off to pull the motor and replace/rebuild it.
If you want to repair it in the truck, you're looking at all the timing components on the front of the motor, possibly heads/cams, roller followers, lash adjusters, gaskets, fluids, and probably a couple of tools you'll need if you haven't done this before. You would be putting all this on top of a 200k mile bottom end that probably could use a freshen up.
Strong case for a crate motor here.

 

[Brons2]

Pretty sure your factory oil pressure gauge is just actually a switch. I think it's 7? psi switch, good gauge reading only means more than 7. Maybe 10, maybe 60. It's more like an idiot light than a gauge.
With the mileage on it and having oil pressure issues, you probably would be better off to pull the motor and replace/rebuild it.
If you want to repair it in the truck, you're looking at all the timing components on the front of the motor, possibly heads/cams, roller followers, lash adjusters, gaskets, fluids, and probably a couple of tools you'll need if you haven't done this before. You would be putting all this on top of a 200k mile bottom end that probably could use a freshen up.
Strong case for a crate motor here.

Good point, he might just be bouncing between low and even lower oil pressure. I have always heard exactly what you said, the gauge is really a 7psi switch. The Ford spec for the 5.4 3Vis for minimum 15 psi hot idle but really that's reduced from the prior minimum of 25, that might be another good datapoint for a reman, is to hook up a mechanical oil pressure gauge and see what kind of pressure you have when it's operating.

The thing about locking out the phasers, it buys you time getting out of replacing them, but it doesn't address the oil pressure issues. The latest revisions of the of the VVT solenoids and rocker arms have smaller oil holes, and the latest revision tensioners have better oil sealing o-rings. The stock oil pumps are all aluminum also, at high mileage they tend to wallow out. (The Melling HV pumps have a cast iron backing plate) The OP could possibly have all these things going on.

Since he says he's not DIYing, I think I agree with you about the crate motor, if the rest of the rig is pretty nice and worth keeping. Of course the high acquisition cost for any kind of new or used vehicle nowadays is also a strong case for fixing the one you have.

 

[GaryH]

A long shot, but is it possible the oil pick up tube was knocked out of place from the collision?

 

[JamaicaJoe]

There could be plastic crud from the chain tensioners blocking the oil pick up.

 

[fuzzmanmatt]

Mine did that exact thing for a while, then it spun a bearing. You might get lucky and be able to rebuild it, but if you're not going to do it and have a shop do it, you may as well spend the extra for a reman motor to get installed. Then you know it's going to work, you'll probably get another 100k out of it (until something else fails, anyway), and it'll probably come with a warranty!

 

[The Chairman]

I had a similar issue on a different Ford engine. Turned out to be just a bad sensor.

 

[cassa89]

How wrecked was the truck? If the body was considerably wrecked and now you're having the oil pressure issues you're talking about, I'd consider cutting my losses and looking for something else. Take the insurance money and start over. If you've already fixed the body damage and you're happy with the way everything looks and functions, then I'd consider a new engine. No way I'd drop the ~$3k in a timing job on an engine with 200k miles unless the issues I had was things like phaser clacking, chain slap, or other things a timing job would fix.