Low Oil Pressure - Just the Pump?

TL;DR: Good cold idle oil pressure, drops under higher rpms when hot, goes back up some at idle.  Goes to a normal hot range at idle after sitting for 15mins.  New pump and hydraulic chain tensioners the fix?

Director's cut:

Fresh from the rant thread, the 2v 6.8l V-10 in my Excursion is having some oil pressure problems.  As I pulled in to my subdivision, the oil pressure indicator lit up as I hit the throttle but extinguished when I let off.  Assuming it was the sender switch, I carefully limped it about a quarter mile into my driveway.  Hooking up a mechanical gauge, though, showed me that at cold startup I had 60-70psi but it would drop to zero if I revved the engine.  I had just checked oil level that afternoon and it was right between the low and high marks.  Oil was 2k miles old synthetic with a Wix XP filter.

Dumped the oil into a brand new pan and it looked fine - no chunks, no glitter, no sheen, no metal bits or chunks.  Cut open the filter and it was also completely clean.  A sample of the oil is sitting in my mailbox right now to be picked up for analysis.

New oil and filter and now it still drops with increases in engine speed, but "only" bottoms out around 15psi.  Again, at cold startup it holds 60-70, increasing about 10 psi when I blip the throttle.  As it warms up, though, holding rpms at about 2k causes the pressure to fall, but it holds a little higher with the fresh oil. at idle it returns to around 20psi.  If I shut it off and wait 15 minutes, the pressure goes back to about 30-40 at idle.

I dumped a large can of seafoam in yesterday and let it idle for a bit to try to clear out any sludging that might be in there.  Need to drain the pan and get my camera in there to look at the pickup still.

All the oil pressure problems I've seen before were low or zero at idle but would inch up with more revs.  And a "reboot" of the engine wouldn't bring pressures up.

Ever since I bought it about 30k miles ago, it has had an intermittent noise that sounds like HLA noise on a Miata.  I know it's not equipped with HLA, but that's the sound.  Anyway, it happens when it's cold and it comes and goes.  Driving down the road or just idling it will start making the noise and then just stop.  It also sounds a lot like the typical Triton exhaust leak.  I figured it was an exhaust leak that closed up with thermal expansion.  Maybe that is a symptom of something related?

Also, about five minutes before the oil pressure idiot gauge started acting up, the truck started making a noise that was almost like a whining or whistling noise.  I thought it was drivetrain related, but it has done that again a little bit in the driveway while I've been testing.

I pulled the left valve cover to check for clogged drains and they were all clear all the way to the pan.  The cam lobes have developed a little pitting but they're not getting flattened.  I don't know how tight or loose the timing chain is supposed to be.  I was going to pull the right valve cover today to have a look-see.  It's always made a bit of a marbles-rolling-around sound that I attributed to A/C clutch, accessory pulley, or heat shield rattling.

I was planning to order up a Melling high volume pump and a new timing chains/guides/tensioners set and tear in to the front of the motor.  But do I need to go further for this sort of thing?

That sounds like the pressure bypass sticking based on the first paragraph.

I have never, ever seen an oil pump be the cause of low oil pressure.  Ever.

Further:  If the oil pump IS ever bad, it is because FOD from the rest of the engine wrecked it.  If you got no glitter, you got no FOD.

IIRC, they use an o-ring to seal the pickup to the pump.  Possibly a torn o-ring that magically lets it suck air when it's hot?  Or a crack in the pickup tube that gets bigger when it's hot?

Stuck bypass sounds plausible, but I'm 80% sure the bypass is in the filter.  Possibly fixed now that you replaced the filter?  That's too easy, but possible.

The filter bypass wouldn't cause this, but a sticky or leaky pressure relief valve on the pump can definitely cause low pressure (by releasing oil back to the pan when it shouldn't).  Pickup tube leak is also possible. 

Typically a pressure drop with increased revs is a pump intake issue.  Either a leak or a restriction.  The other thing that can cause that is an over filled sump where the crank is frothing up the oil.  I've never been in one of those engines so I can't help with specifics.

In reply to APEowner :

If you've been in a 4.6L or 5.4L, it's the same thing but two extra jugs on the end.

Could the HLA-like noise be coming from the cam phasers? I admit to forgetting almost everything I learned about the mod motors since owning a 2005 F150 with the 5.4L about 15 years ago. 

Hydraulic timing chain tensioners?

I also haven't ever heard of an oil pump just failing without having first ingested something.  I was also leaning towards something blocking the pickup tube or the pressure relief valve sticking - and I'm fairly certain that the valve is built in to the pump. 

One of the problems I've had in my research is that I guess these motors don't fail that much.  The other Triton motors which are basically the same minus a jug on each side like Curtis says have things like cam phasers which are common failure points and get a lot more Internet attention, apparently.  I came across a few stories of the hydraulic tensioners failing by leaking past their seals, but from my reading that's a problem with plastic-bodied ones and I'm pretty certain that mine are cast iron.  But I figure I have to take the chains off anyway so for a buck-fitty I might as well put new chains, tensioners, and guides on, if nothing else to hedge against the tensioners. 

Unfortunately, dropping the pan involves lifting the motor up since someone installed a crossmember and a transfer case under the engine, otherwise I would already have the pickup removed and inspected.  It looks like the pump job can be done without lifting the engine, although the pickup bolts are a bit fiddly.  I figured I could pour some diesel fuel down the pickup tube and blow some air through to backflush it a bit once the front of the engine is opened up.

This motor doesn't have the cam phasers and the problems that those bring.  The only "common" issue that I'm aware of on the 2v 6.8l is the uncommanded high-velocity spark plug removal which seems to be fixed by over-torquing the plugs to about 28 ftlbs.  Oh, that and the manifold studs causing exhaust leaks that sound like HLA noise or sometimes rods knocking.  Ah, and the COP modules failing so much that it just makes good sense to drive around with an extra coil and a 7mm wrench in the glovebox.  But, none of that affects oil pressure.

Oh, for your viewing pleasure, this is the view of the oil pressure gauge after I got it hot, watched the pressure bleed down to around 15psi while revving, shut it down, let it sit for 15 minutes and re-started it.

My bet is on sucking air.  Especially given the delay.  It blips up with RPM, then falls.

Oil fill tube O-rings can do weird ish like this when pinched or damaged.  Not a clue on a blue oval.

In reply to 84FSP :

That's easy enough to check.... overfill the engine, jack up the back end as high as you can, and see if it still does it.

Pete. (l33t FS) said:

In reply to 84FSP :

That's easy enough to check.... overfill the engine, jack up the back end as high as you can, and see if it still does it.

What he said.^

I'm going to suggest that the pan is going to end up on the floor at some point.  A gerotor (?) pump almost always winds up with some of it below the front lip of the pan, but I don't recall having a modular Ford apart, so I can't say.

It really sounds like its sucking air somehow.

I buttoned it back up and let it idle at temp for about 30 minutes to circulate the seafoam.  It held just above 50psi for most of that time.  When I started giving it some revs, it started to act normal but then under sustained RPMs it started dropping again.  I guess the only other thing I can do is dump this oil and try to get a look at the pickup tube.

Oh, and since it's already parked at a pretty jaunty angle in the driveway, I can also try to overfill the pan.

wae said:

I buttoned it back up and let it idle at temp for about 30 minutes to circulate the seafoam.  It held just above 50psi for most of that time.  When I started giving it some revs, it started to act normal but then under sustained RPMs it started dropping again.  I guess the only other thing I can do is dump this oil and try to get a look at the pickup tube.

Oh, and since it's already parked at a pretty jaunty angle in the driveway, I can also try to overfill the pan.

I'm not sure it's worth trying over filling the pan.  If it doesn't fix it you don't know if it's because the problem isn't a pickup tube leak or if it's because the crank is aerating the oil.  If it does fix it, then what?  You still need to pull the pan to fix it.

This is what Ford has to say about NON-Ford filters and Warranty work.

Engine Damage / Non-Ford Oil Filters - All Model Years, All Vehicles A review of warranty claims indicates that engine damage caused by defective non-Ford oil filters is being claimed under Ford warranty.

The check valves in some non-Ford filters disintegrate causing small rubber debris (frequently red color) to migrate into the engine's oil passages where they restrict flow. This restriction causes components (such as the variable cam timing phaser) to fail, and causes engine knocking / ticking /rattles. Please reference: SSM #18921 (Published: 11/03/05) SSM #19642 (Published: 03/01/07) TSB #06-19-08 Repair of engine damage caused by defective non-Ford oil filters is not covered per Section 3 of the Warranty & Policy Manual. Category: Powertrain – Engine Do: Look for bits of rubber (frequently red color) when repairing damaged engines.

Not sure if I can believe the above 'info', but trying a genuine Ford oil filter might be worth a try. You might also try running thicker oil

Also note that several Ford Triton engines (not sure about the V10 tho) seem to be known for early oil pump failures. There are a more than a few web articles and posts on the subject of Ford low oil pressure problems.

In reply to FMB42 :

I have actually come across that before and tracked down the TSB that is referenced there, although I've not been able to find the SSM documents.  The TSB make reference to - and I'm paraphrasing here - off-brand oil filters not commonly seen in the marketplace.  It is entirely plausible that there was some bit that got loose way back before I owned it and it moves around from time to time causing the very intermittent ticking noise.  And now one of those bits has finally gotten lodged in such a way that it's causing a consistent problem.  I've always used either a Wix XP or a Bosch filter on it, but the first hundred thousand miles are anyone's guess.  I'm a bit hesitant to try running a thicker oil, though, because of the tensioners.  There's a lot of info out there and it's hard to pick out what applies to the 2v, 3v, and 4v motors and how much cross-pollenation there is from the 5.4/4.6/6.8, but blowing out the seals in tensioners is apparently a somewhat common issue in the general population of "Ford Mod Motors" and that can be exacerbated with thicker oils.

There are a lot of oil pressure problems out there and a boatload of them are related to the sender failing and not actually having low oil pressure.  Once I filter those out, though, most of the remainder are situations where the low oil pressure was persistent enough to spin the bearings so those stories all end basically the same: Chunks of metal in oil, replaced engine, didn't tear down to determine what failed.  Not to be selfish or anything, but that lack of willingness to do a post-mortem really doesn't help me.

At this point, I'm going to hold off on any more diagnostics until I can get it over to the shop.  I need the garage space today and tomorrow so I'm thinking that I'll have it towed over on Wednesday.  Because of the angle required, I don't think the tow operator will appreciate me trying to convince him to unload the truck directly into the garage so I planned to have him drop it in the lot and then I'll just drive it in - especially when cold it keeps enough oil pressure at sub 2k RPMs that I don't think I need to worry about it.  So I don't really want to futz around with adding or draining oil just to have to put it back in again to move it and then drain it all back out.  And it's a good point on testing the tube.  If that oring is bad, I'll have to open it up to replace it.  If over-filling it doesn't solve the problem, I'll need to open it up to check and replace the tensioners and pump/relief valve.

I have been trying to better organize the version of the factory service manual that I found on-line by transforming all the white-on-black diagrams to black-on-white and cutting out the bits I don't need.  I'm not sure how necessary it really is, but according to the FSM, they want me to raise the engine to do the right side valve cover.  So that's fun.  It's certainly got a lot more stuff in the way, but I haven't taken a real hard look at it yet.

I'm putting bets on a leaky pickup or a partially clogged pickup strainer as well. RPMs go up, pump is trying to pull more oil through the pickup, and the increased pressure drop causes the seal interface to become the path of least resistance and start pulling in air instead of oil. As soon as air gets to the pump, it cavitates and loses pressure/prime.

It is a little odd that it is fine when cold, since I would think the oil being more viscous would make it more likely to pull in air. One of my buddies just did this fix on his 6.0 LS with basically the same symptoms and it completely resolved the problem, though.

The pressure relief would act exactly like this.

I'd still be digging into where the prv is and how it functions in this engine.  Your symptoms sound exactly like a sticking pressure relief valve.

Note:  not the filter pressure relief.

Yeah, the pressure relief valve is integral to the oil pump itself on these so there's no real way to look at it without tearing the oil pump off the crankshaft.

I got the pages from the factory service manual organized yesterday and the crank and cam hold down tools all arrived as well. 

Something that the truck has always done is make a bit of a noise at idle - maybe it makes it at higher rpms, but I can't hear it over everything else.  It always sounded to me like an accessory pulley bearing or A/C clutch bearing that was starting to get kind of gravelly but it's not changed at all.  While the truck was just idling around the other day and the only other thing I had to do was watch the oil pressure, I whipped out the stethoscope and listened around a bit.  It really sounds like it's coming from under the left valve cover and all of the accessories are actually pretty quiet.  I'm wondering if maybe one of the rollers are failing or if the balance shaft has too much play.  So I got to thinking about checking those while it's out and maybe looking in to picking up a replacement cam from the junkyard since there's some pitting on the lobes.  You know, just "while I'm there" stuff.

According to the FSM, in order to remove the camshafts, the intake manifold has to come off.  Which kind of sounds weird to me.  I didn't look at it that hard when the cover was off, but I don't recall seeing anything in the way of the cam caps.

Oh, and the lobes in question:

And yeah, that picture looks all smooshed up...

In reply to wae :

Picture looks fine to me. Chrome on windows desktop.

Second time in less than a month that the B.U.T.T. has been on the back of one of these trucks.  Oy.  Drove it up on to the ramp and then back down off the ramp an in to the garage.  Held 70psi of pressure through the whole process.  Now I just need the parts to show up.  Some days the FedEx guy will just leave the package at the door other days he won't.  I don't know what's up with that...

I agree with gearhead that a leaky oil pump pick up could be the cause. I've seen this only once, but it was definitely the problem in my case (i.e. somewhat low oil pressure). However, this problem was due to a bashed in/up oil pan.

In reply to FMB42 :

Leaky oil pickup O-ring usually happens around 180-200k miles on GenIII/IV Chevy engines.

The usual gang of morons on iATN will say just replace the engine, it's probably all berkeleyed inside anyway.

People who actually REPAIR things instead of pontificate online will note that replacing the O-ring brings oil pressure back up to spec.

As far as Ford Mod motors go... I dunno.  Ford rust out before they have engine problems up here.