Diagnosing low oil pressure (EJ22)

[jonathan909]

So I got the call from my wife last night during her commute home - her '98 Legacy DD's idiot light went on.  Under the misapprehension that the light means "time to add some oil" and not "stop right g0dd@mn now", she continued to drive to the next convenient gas station, then dumped in a couple of overpriced litres without first checking the dipstick.  She phoned me when that failed to turn off the light.  (It's now very overfilled.)

After I stopped yelling...

I drove into the city and picked her up; there's a call in for a tow, which should be some time today - response times are rather long at -30 degrees.

I've never had to debug low/absent oil pressure in one of these things, and could use a little guidance:  How to go about it without risking (further) damage?  And is there a convenient port where I can connect a (mechanical) gauge for diagnosis, or do I have to unscrew the existing sender?  This is going to be hard enough with the low ambient temp, so I really want to make sure I don't screw up.

 

[1 Lucky Texan]

did she report any clacking/ticking noises too?

the OP switch/sender is kinda under the alt. That thing comes on at something like 4psi. If she overfilled though, maybe she still had oil flowing?

 

I suppose we're sure it was the oil light and not  - what? ABS or CEL, etc.?

 

anyway, hope the car is OK.

 

[jonathan909]

I had to run it for a minute or so because she'd parked it in a bad spot (in front of the gas station's dumpsters) and it needed to be moved to where it could wait for a day.  It's definitely the oil pressure light (which came on maybe 10 seconds after the engine started).  And I didn't detect any obvious bad noises e.g. a spun bearing, so I have hope.

I know where the sender is; I'm curious whether that's the only available port I can use for a diagnostic gauge, or whether there's another easily-accessible plug somewhere.

But my larger question is about diagnosing the cause of the problem without risking (further) damage.  How to proceed?

[1 Lucky Texan]

long ago at nasioc I had read of an alternative plugged port but, not even sure of what engine was being discussed.

hopefully, GD ( @GeneralDisorder  or some other guru can respond - I suppose there's no reason not to use the sender's port but, there are pancake (or is it waffle?) adapters that can go under the oil filter.

sometimes the soobs from the 90s can have leaks on the back of the oil pump from screws loosening.

on rare occasions, some soobs in the early 2000s have suffered cracked pick-up tubes.

 

that's about the extent of my help though lol!

Edited February 12, 2019 by 1 Lucky Texan

[nvu]

Sender port is the simplest for a temporary install if you want to diagnose the problem.  You could remove the alternator belt and swing it out of the way.  The car could run for an hour before batteries get low.  

It's likely just the sender, the engine would already make bad noises if it were actually low pressure while driving.  With the engine warmed and real pressure gauge attached, rev it a bit and see if the pressure stays good.

Edited February 12, 2019 by nvu

[GeneralDisorder]

It's likely a bad sending unit. Since I've almost never seen an EJ lose pressure while running and full of oil.... I guess the only possibility there would be a completely plugged or broken off oil pickup tube. 

But yes regardless of the reason.... the educational take away here is you MUST shut off the engine as soon as is safely possible to avoid potential damage. 

GD

[FerGloyale]

Either the pickup screen is clogged with carbon deposit, OR the backing plate of teh oil pump is coming loose.  If that's the case, you need to pull the timing belt and pull the oil pump off and check it's backing plate.

Verify pressure with a gauge at the sender port.  If low pressure, then inspect the oil pump.  Good time to do timing belt if it needs it.  If pump is good, then pull oil pan and inspect pickup tube/screen.

[Numbchux]

15 hours ago, GeneralDisorder said:

It's likely a bad sending unit. Since I've almost never seen an EJ lose pressure while running and full of oil.... I guess the only possibility there would be a completely plugged or broken off oil pickup tube. 

But yes regardless of the reason.... the educational take away here is you MUST shut off the engine as soon as is safely possible to avoid potential damage. 

GD

I agree, most likely pressure switch

 

11 hours ago, FerGloyale said:

Either the pickup screen is clogged with carbon deposit, OR the backing plate of teh oil pump is coming loose.  If that's the case, you need to pull the timing belt and pull the oil pump off and check it's backing plate.

Verify pressure with a gauge at the sender port.  If low pressure, then inspect the oil pump.  Good time to do timing belt if it needs it.  If pump is good, then pull oil pan and inspect pickup tube/screen.

 

But, if it's actually low pressure, and it has plenty of oil. These are the things to check. I think I'd check the oil pump first.

[jonathan909]

Gents, thanks for the input.  I found I had a spare sender lying around, and all things considered, trying it involved the least time spent outside.  Appears to have taken care of the problem.

Now, to draining the excess oil... and giving the SO an education PDQ in how not to FSU.

 

[FerGloyale]

29 minutes ago, jonathan909 said:

Gents, thanks for the input.  I found I had a spare sender lying around, and all things considered, trying it involved the least time spent outside.  Appears to have taken care of the problem.

Now, to draining the excess oil... and giving the SO an education PDQ in how not to FSU.

 

hmm....I would want to see some #'s on a gauge.

if the light comes back on again, I will bet for sure the pump backing plate is loose.

[jonathan909]

1 hour ago, FerGloyale said:

hmm....I would want to see some #'s on a gauge.

Mos def.  Given the immediate circumstances, though (it's my wife's DD and the present weather isn't compatible with doing any more than absolutely necessary), I'll settle for "light not on".

Besides, I need to get a fitting for my gauge.

1 hour ago, FerGloyale said:

if the light comes back on again, I will bet for sure the pump backing plate is loose.

With any luck I won't need to find out anytime soon.

[jonathan909]

1 hour ago, FerGloyale said:

if the light comes back on again, I will bet for sure the pump backing plate is loose.

Incidentally, I can't be the only person here filled with blind hate for the philips-variant screws used here and on the separator plate and wrist-pin port.  I'm pretty well strapped with the right tools, but have never been able to avoid chewing up those heads.  Bought a big bag of socket (allen) head screws as replacements and do so at every opportunity.

[FerGloyale]

1 hour ago, jonathan909 said:

Incidentally, I can't be the only person here filled with blind hate for the philips-variant screws used here and on the separator plate and wrist-pin port.  I'm pretty well strapped with the right tools, but have never been able to avoid chewing up those heads.  Bought a big bag of socket (allen) head screws as replacements and do so at every opportunity.

#3 bit in an impact driver

works every time

https://www.homedepot.com/p/Powerbuilt-7-5-in-Impact-Driver-Kit-648002/204505142?cm_mmc=Shopping|G|Base|D25T|25-1_HAND+TOOLS|NA|PLA|71700000034127224|58700003933021546|92700031755124841&gclid=EAIaIQobChMIrrmN28S54AIVCtRkCh2FaAYLEAQYBCABEgK7HfD_BwE&gclsrc=aw.ds

As an alternate, if you have just a #3 phillips bit, you can hammer that sucker in there.  Then try turning with a socket on the bit.  Helps seat it deep, and the shock from hammering on it often unsticks the screws.

[Numbchux]

Yep, Impact driver. For Christmas I got a pair of Craftsman impact screwdrivers (functions the same, but looks like a normal screwdriver). Looks pretty cool......I haven't used them yet, though.

[idosubaru]

This:

2 hours ago, FerGloyale said:

#3 bit in an impact driver

works every time

https://www.homedepot.com/p/Powerbuilt-7-5-in-Impact-Driver-Kit-648002/204505142?cm_mmc=Shopping|G|Base|D25T|25-1_HAND+TOOLS|NA|PLA|71700000034127224|58700003933021546|92700031755124841&gclid=EAIaIQobChMIrrmN28S54AIVCtRkCh2FaAYLEAQYBCABEgK7HfD_BwE&gclsrc=aw.ds

As an alternate, if you have just a #3 phillips bit, you can hammer that sucker in there.  Then try turning with a socket on the bit.  Helps seat it deep, and the shock from hammering on it often unsticks the screws.

Those things are awesome time savers. I can't  imagine how much time I would have lost in the rust belt without one.

3 hours ago, jonathan909 said:

Incidentally, I can't be the only person here filled with blind hate for the philips-variant screws

Bought a big bag of socket (allen) head screws as replacements and do so at every opportunity.

A blind hate for rust, yes, not the fasteners.   I hate allen heads - they rust and round out all the time and then require more tools.  They seem to respond worse to alternative methods of removing once they rust/round out, but maybe that's just because there's fewer of them in Subaru world and i have less experience. 

[GeneralDisorder]

Socket head allen is great because when it strips out you already have a perfectly centered pilot hole for your left hand drill bit. 

Incidentally though, Torx is better and triple square is even better still. They have higher torque ratings and more positive engagement than either allen or phillips. I think at least with Torx you can pretty much replace any of the Phillips fasteners. 

Although you don't even need the impact screwdriver - just hit each one with a hammer and punch and they will generally come right out. The impact screwdriver is nice though. All in one tool. 

GD

[jonathan909]

7 hours ago, idosubaru said:

This:

Those things are awesome time savers. I can't  imagine how much time I would have lost in the rust belt without one.

A blind hate for rust, yes, not the fasteners.   I hate allen heads - they rust and round out all the time and then require more tools.  They seem to respond worse to alternative methods of removing once they rust/round out, but maybe that's just because there's fewer of them in Subaru world and i have less experience. 

Well, the conversation started with a discussion about oil pumps - about the last place where rust is an issue.  I don't have a universal love for Allen heads - they get worse as they get smaller.  I've used them all the way down to .030" (or maybe .035" - I'd have to check), and down there the engagement and torque are almost nonexistent.  But up at these sizes they're tolerable, and preferable to "Philips", because at least a hexagon is always a hexagon.

The problem with Philips is that they usually aren't - that is, there's a buttload of different heads that all look more or less like Philips, but the tooling doesn't interchange between them worth a d@mn, making every time you apply a driver to one a crap shoot as to whether it's gonna move or the head is gonna chew.  To make matters worse, the sizings come in both imperial and metric, making it even harder to get the right driver.

https://en.wikipedia.org/wiki/List_of_screw_drives#Cruciform_drives

Worst.  Head.  Ever.

Edited February 14, 2019 by jonathan909