Mysterious Oil Light, Gremlins?

[alphamikefoxtrot]

Bought '00 4R SR5, 216k miles, spotlessly clean body, frame, interior, etc. Performed preventative maint. week following purchase; water pump, timing belt, valve cover gasket, front rotors and pads. Driving to work (30 miles highway) next day oil light comes on, engine temp fine, oil quantity fine, no rough running / knocking. Driving later that evening after cold start, no light, following day on the way to work, light on again. Replaced sending unit, no change in light behavior.

Purchased from dealership, they had changed oil prior to me taking posession - my supposition is that their oil is too thin, considering having changed to bottled-oil vs. barrel, adding oil stabilizer (reccomendations on which one?)

Eager to hear your thoughts!! Thank You!

Moderator(s) please feel free to re-position this post as you see fit.

 

[haddix]

Bump for ya..

 

[DC runner]

It is 1 of 2 things.

You changed the sender sensor, so I would rule that out. That means either a. your oil pump is on the way out and no longer able to pump oil at the correct pressure or you have a clog/sludge build up in the engine that is creating a pressure pinch.

Both create the same thing. Too low oil pressure. In my experience, the dealer was just throwing something out. A variation of 10 on the weight scale would not have any noticeable impact on a healthy pump/engine in terms of pressure.

Their excuse sounds B.S'y to me. I had a similar situation and in mine it was sludge.... the Toyota's have been known the have a sludge build up problem. You need to get an actual read on the PSI going through. Get a gauge and attach it where the oil sender unit is...


Edit: Never mind, you are arguing to thin. Nah. Minor difference, if any. It is oil weight that matters, not where it comes from. Your talking at most a difference in 1 or 2% and that would not do this. I bet you it is a pressure issue from either the pump or sludge.

 

[alphamikefoxtrot]

See the odd thing is I'll have no light for the first 30 minutes of driving, then it'll come on, flicker, then stay on. Occasionally it'll go on when I back off the throttle / off when I advance the throttle, indicating to me that it's pressure-related. Oil level, engine temp, and idle / run are all nominal. Ideas for killing sludge build-up if that's the likely culprit? Thank You!

 

[sabre65]

See the odd thing is I'll have no light for the first 30 minutes of driving, then it'll come on, flicker, then stay on. Occasionally it'll go on when I back off the throttle / off when I advance the throttle, indicating to me that it's pressure-related. Oil level, engine temp, and idle / run are all nominal. Ideas for killing sludge build-up if that's the likely culprit? Thank You!

I have a occasional knock at idle in gear (engine hot after a drive at highway speeds). I hooked up a mechanical guage and showed 80 psi at cold start up and 25 to 40 psi at hot highway speeds (or running the engine around 2000 rpm. Hot idle was between 5 and 10 psi in drive. The Toyota techs can't agree on the knock and the darn thing runs great. Keep us posted as I'm due for tires and don't want to spend more money on this one if it's engine time.

 

[Drcoffee]

Change the oil filter immediately. The media maybe collapsing under pressure. If that doesn't work, run some sea foam in the oil and then change the oil to synthetic. The synthetic will clean out the passages and flow where conventional may not. If it still persists, the pump is likely beginning to fail. In any case I would not suggest that you keep running the truck with the light on. You have already ruled out a bad sender and you now know its a low pressure problem. When that light comes on, you are starving the motor for oil. I think the light comes on when the psi is below 10#. Don't be shocked if your engine seizes while you are driving. You've been warned.

One more possibility that comes to mind is the piston rod bearings maybe failing and the journals have widened. As the oil thins out as it gets hot, it leaks out from the bearings and that's why the pressure sender is registering low pressure. Are you hearing. Any knocking?

Try some snake oil like ZMaz in the oil. If nothing else it may help prevent the bearings from grinding down without oil.

 

[Drcoffee]

I have a occasional knock at idle in gear (engine hot after a drive at highway speeds). I hooked up a mechanical guage and showed 80 psi at cold start up and 25 to 40 psi at hot highway speeds (or running the engine around 2000 rpm. Hot idle was between 5 and 10 psi in drive. The Toyota techs can't agree on the knock and the darn thing runs great. Keep us posted as I'm due for tires and don't want to spend more money on this one if it's engine time.

Somewhat irrelevant but google "jeep low oil pressure" and you'll find a lot of similar complaints. The engines run fine even with low pressure at idle. I dont know if the t4r is as forgiving. The difference here is that the jeep's oil pressure is only low at idle. Try a thicker synthetic oil that won't thin out as it heats up. Amsoil would be my choice.
I think you will be okay as your pressure is within spec while driving.

Good luck

 

[TRD 2.0]

still have low pressure

Hey guys,
I've been battling with the same issue. Right around new years, I noticed that my 'low oil pressure light' was coming on once the engine was warm and mostly only at low RPMs. It seemed that once I hit the accelerator and RPM came up, then the light went out. Well I did some research and ultimately had it diagnosed and it came back as a failing oil pump. I went ahead and did the new pump and new pressure sensor. When I had the oil pan off, I inspected everything pretty good, and didn't notice a lot of build up or anything, it seemed pretty clean inside the block. The issue I am still having, is that silly light is still trying to flicker on me again :-( I am beginning to wonder if I should try to switch to a synthetic oil or what might be causing this? It's a 1998 SR5 3.4 5VZ-FE engine 4x4 with about 187,000 miles.
Anybody have any suggestions or advice?
It would be much appreciated!

 

[Singtoe]

sounds like the oil pressure relief valve is malfunctioning. Try remove it, check it out and reinstall.


A temporary fix will be to use a thicker weight oil - 20w-50