Just picked up a 2003 Tacoma 5vx-fe 4x4. 204k miles... engine sounds good to my untrained ear with the exception of what I think is power steering squealing for a while when I start up.

Few days ago the oil pressure light started flickering on off. I stopped car, listened and heard no concerning engine noises or knocks. Light went away after turning off and on but after more driving came back on.
I changed the oil pressure sending switch next day and did more driving After 30-45 mins of driving the oil light appeared again with new sensor but no engine noises or knocks. Would go away and stop/start of motor. I purchased an oil pressure tester from Harbor Freight to check things out. After connecting oil pressure gauge the pressure started high 50 PSI or more. As truck idled and warmed up it eventually got down to about 10 psi. Reving to 2-3k rpm I saw gauge rise to 25-35 psi.

I threaded the pressure gauge through the firewall and went for a drive to watch the pressure. Pressure slowly started to decrease from 10psi towards zero. Reving to 2-3k rpm didn't increase pressure. So now I'm really concerned.

I put truck in neutral, turned it off and coast a 30 secs or so and turn back on and oil pressure was 10psi at idle and raising to 25-30psi at 2-3k rpm. I drove for a while and it slowly lost pressure and repeated turning off motor and then back on and pressure would seem normal.

What might I be dealing with here? Bad motor? Strainer picking up sludge, trash? Bad oil pump? I'm far from a subject matter expert. Please help!

 

Doesn't sound good if its going to zero, 10psi hot at idle is normal for most vehicles, but the first thing I would do is change the oil into a clear or white bucket and maybe open up the drained oil filter over some white paper. What oil weight are you running, what oil filter is on it, I personally run Castrol Synthetic 5w30 and the larger 2nd Gen Tacoma -D3 OEM oil filter, I wouldn't touch some of the aftermarket filters available nowadays with plastic filter cages inside. Depending on the temperature outside maybe it might be wise for you to try 10w30 Dino oil and an OEM filter just to see if you notice any changes.

Some of those aftermarket belts squeal no matter how tight you get them, usually the ALT belt, again OEM is best here, I think they are Bando or Mitsuboshi.
Bando 4PK-0870 AC
Bando 4PK-1050 ALT
Bando 4PK-1070 PS
OEM
99364-20870-78 ac belt
90080-91126-83 power steering
90080-91090-83 alternator

 

thx for feedback. I haven’t changed oil yet. When I purchased this truck a few weeks back the oil looked and smell ok. I just got a couple gallons of 5w 30 synthetic from Costco and will get a few filters in anticipation of a few changes in near future.

Ultimately I think I will need to drop the oil pan which is a big job.

 

<<< Shows oil pressure looking normal

 

That looks good and normal, now lets see the drop off in oil pressure while it coincides with the oil light for entertainment. Is that an electronic gauge with sending sensor, it would be nice permanent addition for peace of mind, you wouldn't wanna run an oil pressure line inside the cab except for testing purposes. If its dropping off I would assume oil pump gears worst case and best resolved asap, if you dive into valve covers it will give you an idea of the oil change frequency, there have been reports of sludge build-up on the 5vz-fe due to infrequent oil changes and/or poor quality oil and I'm sure thats not good for oil pump gears and oil ports if any breaks loose.

 

from you description of slowly losing oil pressure until you shut the truck off, then everything starts back up normal... that sounds like it's slowly getting plugged and then when there isn't any suction because the truck is off all the goo dislodges and drops to the bottom of the pan.

You can get a cheap Harbor boroscope and look in the pan during an oil change. You can also seafoam or kero the oil for a few minutes and do a fresh oil change.

In any case, loosing oil pressure should be addressed sooner than later. Once you get an engine noise like knock... they don't go away.

 

Here is a vid showing problems. Didn’t drop to zero here but something definitely is off.

 

Check out vid I posted. Not going to zero in this example but this should give you an idea of the behavior. This gauge is mechanical. It’s engine/tranny test kit from Harbor Freight. It was very helpful to run inside and drive the car. Once I get this resolved I will likely invest in cluster of electrical gauges. Thx again for guidance

 

Hope to pull passenger side valve cover this week for a peak.

 

Thanks for feedback. Good suggestion on scope and I may be able to use it for other projects!! Been considering kerosene/diesel/seafoam/ATF. Some suggest filling up to oil cap and sit overnight then drain without running. I've had good luck with soaking old sewing machines with kero to kill the crud. Kero doesn't dry them out and leaves a nice thin oil coating.

 

I would NOT fill the entire motor with kerosene. That’s asking for trouble, when you try to circulate it around.

 

Well it didn't drop off to zero, motor sounds healthy, and you don't have the engine under load/driving, also oil pressure gauges can be finicky and not 100% accurate but should be consistent with RPM's so the drop out under higher RPM's is concerning meaning oil is bypassing the bearings, weak oil pump or a plugged oil pickup, again all guessing., so mainly watch for consistency as the gauge could be off by 5psi. There is a thin baffle in front of the oil fill hole you're seeing that tends to get a little cruddy,, but yours does look a lot worse than most I have opened, especially with the sludge being in the oil cap. Wouldn't hurt to do a compression test just to see how the engine is doing in that regards, might help with decision making as you go as well although not related to oil pressure. I'd say maybe where you plumbed the oil line in could be a bad spot but since your new oil pressure sensor is still flagging the warning light, we know you have oil pressure/loss issue.

You can run 1L of ATF in the oil to help clean it out but I wouldn't drive it hard since you have oil pressure issues, maybe leave it in a week then try an engine oil flush, best would be to use the engine oil flush, but never drive it with engine flush in it,(seen people do that and then replaced the piston rings) just rev it up to 2000RPM's for 5 min usually-follow instructions on bottle and drain. Personally I would try 10w30 or 10w40 DINO OIL and OEM filter after the flush and see if there is any change, but it would be a bandaid fix for the time being until you make a plan of attack to sort it out or cut your losses and find another 5vz-fe if oil is bypassing the bearings or the compression is low, oil pump gears might not be to terrible, but you'll have to lift the engine a bit to sneak the oil pan out.

 

The posts I read of people doing this let it soak only then drained. They never started it up. I'm pretty far from doing anything like this right now.

 

I should clarify that I've removed the new oil pressure sending unit and plugged the mechanical testing gauge there. I now understand I can pop out one of those other plugs near the sending unit and use that for my gauge.

I didn't get footage of it going to zero while driving but it certainly get very low on that gauge.

One new concern is this high pitch squealing on a cold startup. It may not be the power steering as I originally thought. To further isolate I'm going to remove belts and start the engine.

Again... Appreciate the insight.

 

Without the oil fill level being too low - and the gauge action doesn't seem to indicate that, dropping pressure like isn't a good sign.
1) Worn bearings - the motor would really need a complete rebuild. Not incredibly likely at 200K, but possible if it has been heavily neglected much of it's life so far. But consistent with dropping oil pressures when hot.
2) Partially clogged oil intake screen - although this would likely not get better when cold, worse when hot.
3) Worn oil pump - luckily enough you can get to this on a 5VZ by taking the front of the engine off, it's down on the crank snout behind everything.

As already suggested, I'd run the motor to mix the oil up well, then drain it all out fairly quickly - to keep small particle sin suspension. And then look for any... stuff... in the oil. Hopefully you won't see shiny bits. Look for possible floating crud that might be periodically clogging the oil pump inlet screen. If nothing turns up, then I'd start tearing into the engine, going in reverse order of my list (reverse order of difficulty).
- pull the front end of the engine off, take the iol pump off, see if that look messed up, worn, damaged.
- if that looks entirely serviceable, pull the oil pan off. This will come off with the engine in the car, I think you'll have to pull the front diff (which is NOT fun). Then look at the oil pickup tube screen. Wiggle the rod bearings, maybe pop a cap or two off to eyeball the bearings.

 

So over the past couple days I added seafoam to the oil. Started with 1/2 can and let idle for 30-45 mins several times over two days. I added the other 1/2 can and allowed truck to idle 30-45 mins a few times. Lastly I let truck get up to temp and and drained oil. I don't see any indication of chunks of crud or glitter in oil, but my eye is untrained. I will reinspect oil tomorrow and cut open filter. .

I filled with 5w30 and a put on Toyota filter. I drove around for an hour and the oil pressure behaved much better than previous drives. I will likely add more seafoam and do some driving and change oil at least 2 more times.

I can't really get up past 50 for long because on the next problem I will tackle, shaking/vibration.

Appreciate all the guidance and input!!!!

 

So over the past couple days I added seafoam to the oil. Started with 1/2 can and let idle for 30-45 mins several times over two days. I added the other 1/2 can and allowed truck to idle 30-45 mins a few times. Lastly I let truck get up to temp and and drained oil. I don't see any indication of chunks of crud or glitter in oil, but my eye is untrained. I will reinspect oil tomorrow and cut open filter. .

I filled with 5w30 and a put on Toyota filter. I drove around for an hour and the oil pressure behaved much better than previous drives. I will likely add more seafoam and do some driving and change oil at least 2 more times.

I can't really get up past 50 for long because on the next problem I will tackle, shaking/vibration.

Appreciate all the guidance and input!!!!

 

Oil pressure a bit more consistent after some seafoam and oil change. Lots of driving after change and the gauge never dropped below 5 where as before after a 20-30 min period I was dropping into the black area. I'm cautiously optimistic. Want to do more observation before taking any significant actions.

 

I think the manual says 4psi minimum at idle HOT, and anywhere between 45-75psi HOT at 3000RPM's, again unless its a very high quality oil pressure gauge it could be off by 5psi + or - so now that you see it acting normally, I would put the Oil sensor in place and see if it is satisfied, maybe the oil sensor port was a little plugged up and now with the fiddling you've done it is cleared out, fingers crossed for ya.