Oil Pressure light help

So I have a 2002 Toyota tacoma xtracab prerunner 2.7 that I purchased last December. I drive it to work every day and even on weekends to my part time. All driving is around the city.

About 2 months ago I drove it to another town which requires highway driving. I got to the other town and stayed there for about 2 hours and came back. Everything was good until I got off the highway (driving below 45 mph) and noticed the oil pressure light blinking. I pulled over and turned the truck off to check oil level and everything was good I turn it on and didn't have the light go off anymore.

I replaced the oil pressure switch the very next day thinking that was the problem and didn't see the light go off for the last 2 months. That is until last night where I drove to the same place and on the way back getting off the highway the light started flashing again. Again I pulled over to check the oil level and it was fine I Let it cool off for a minute and turn it on to go home and haven't seem the light again.

What do you think it could cause the light to go off after highway driving.?

(I should mention that I get a squeal in the morning when I turn on the truck. It's almost like a belt sound. but it doesnt do it when the truck is still warm.) Is there a connection between the two?

 

Squeal is probably belt. Have you changed the oil lately? You might need to get/rent/autozone loaner a mechanical oil pressure gauge to check oil pressures

 

A Ghost?
Maybe the oil pump screen is partially sludged.
For example how is the compression on the four cylinders?
Perhaps the previous owner put Slick 50 or some other teflon additive into the engine
and now your oil flow to the pump is borderline restricted.

An easy way to test this hypothesis is to take the pressure switch sender off and connect a pressure gauge
These are manufacturer specs (I believe it should be minimally 10psi per 1000 rpm
It may be low

 

I think that's what I'll do. Thanks.

 

I'll see about getting the pressure tester within the next couple of weeks. You may be right about the sludge I have to take it apart to see it.

I also read on another thread that the oil filter might trigger a low pressure light if you don't use the OEM filter.

 

Maybe the highway driving heated the oil a bit more than usual causing it to thin out, then the oil pump couldn't pump at the same pressure. Normally, the pressure should remain high and the light shouldn't come on even when the oil gets hot, but maybe this is an early warning that something isn't right.

 

Saul,
I have given some more thought to your problem... I have the similar 2003 3RZ-FE
BTW as an original owner with 180k I have always used Mobil1 5w-30.
Hope to never have this problem!

Assuming your oil pressure is low...
Bad oil (DrZ's post), a clogged filter, aerated oil (tiny air bubbles?) from overfilling the crankcase, can all adversely affect oil pressure.
Given that you yourself changed your oil pressure sender I cannot believe that you have neglected any of these. But double check.

Low oil pressure, how to diagnose the cause?
As I already mentioned hopefully the oil pump strainer is clogged.

The oil pumps on these engines are pretty hardy and I doubt that it has failed.
In order to take the oil pan off you will have to drop the differential (a lot of work). Then check the oil strainer for sludge or blockage, lets hope you find some.
If there is none, then I would take a look at your pump, hopefully the cause is not more serious than that.

If you get to this point you may want to take the rig to your trusted mechanic... unless you have the tools, know how and time to take this to the finish.

Worst case scenario... worn main and rod bearings.
Check out this thread:
https://www.tacomaworld.com/threads/1996-2-7l-low-oil-pressure-light-at-idle.68948/#post-11713564

High mileage engines with low oil pressure can be caused by worn bearings.
The oil pump does not create oil pressure, it makes the flow; it is the resistance to flow that produces pressure.
Less resistance means less pressure.
Worn bearings with increased clearances will relatively increase oil flow, causing a lowering of oil pressure.

Sounds simple... it is.

If the bearings are bad, that reduction in oil pressure will probably have reduced lubrication to the camshaft and overhead valve train... causing increased wear and greater clearances there, thus adding to the overall loss in oil pressure.
The cure? replacing all these bearings... a major engine overhaul.

FWIW these engines are so beautiful if treated properly.
It would be worth the investment to start it over should you have to come to this point

 

if the screen is blocked or sludged up there are a couple of things that you could try. If it was me I would take the oil filter off and put a new factory filter on it and cut the old filter open to take a look at what is inside of it. If there are little trapped pieces of crustiness you have a good idea of whats going on inside the motor. Depending on the size of your wallet and if you have a second vehicle to drive I would add some Marvel Mystery Oil drive her and see if it gets and better. A more aggressive approach would be 1 qt of automatic transmission fluid and let her idle for a while. There is a lot of detergent in ATF. Do a hot oil change with a new oil filter and see if this corrects it. The final and most aggressive is 1 pt of brake fluid and let her idle with new oil and filter. DOT 3 brake fluid is so aggressive that it will eat paint. The warning is that brake fluid will also effect oil seals. Like I said, it all depends on how much you want to spend... if she is needing an overhaul due to bearing wear your not going to hurt much by any of the methods above.

 

If you have not changed the oil it might be as simple as a defective filter or one that is collapsing.

 

Not to be a smart ass but I cannot resist...
A 2002 FAA mandated chemical analysis of ca. 1920 "Marvel Mystery Oil" revealed it to be composed of 74% mineral oil, 25% Stoddard solvent, and 1% lard. But it works!

 

I figured MMO had some solvent but 25%... seems kind of high... does the FAA approve or disapprove of MMO?

 

IDK. I'm not a big fan of experimenting with my cars that way. I will however try cleaning the screen manually (if possible) and use an OEM filter next time I do an oil change. I appreciate the ideas though. Your heart is in the right place.

 

It did it with the last two oil filters (k&n). I'm hoping it's just the OEM filter.

 

I replaced all three belts on Saturday so no more squealing. It costs me 50 bucks but it was worth it.

 

I'm missing something.
I thought the problem was low pressure.
How does a bad or blocked filter do anything but increase oil pressure (like holding your nose while you sneeze LOL)?
Oil that is broken down will decrease resistance to flow and lower pressure however.

Cutting open and inspecting the oil filter is a good suggestion, because it may show if the oil pump is impeded by sludge from supplying a normal oil flow.
The filter may also have metal debris, a sure sign that bearings and other critical pressure points are allowing oil to leak and reduce pressure in the system.

If so this will save you Saul from having to go into the engine to diagnose the cause.

 

Neither, it came out of the FAA mandated analysis after a crash landing of a plane that had it in its fuel tanks.
Wikipedia refers to the report here:
https://en.wikipedia.org/wiki/Marvel_Mystery_Oil

 

Oil must circulate. If you have a failing filter I assure you low oil pressure will be the first symptom.

 

This is a very common symptom of a clogged up oil pickup screen. Either way the oil pressure is getting low and it can easily starve for oil, you need to inspect it.

 

something else I just thought of... any signs of RTV anywhere on the motor... oil pan, valve cover(s) etc. Shade tree types really goop it on thick and just as much squeezes inside the motor as outside. After a bit it drops off and finds it way into the oil pan, then pickup screen.

 

Any tips on how much to use?