mstasiewicz

I have a 99 4runner, 158K miles. My kid drives it then tells me the oil light is coming on on the dash. So I get into as I am an Aircraft Mechanic I get into things sometimes real deep. So I replace the oil pump, and oil sender device. When the engine is cold the light is off. But when the engine warms up and I am sitting at idle the oil lights comes on. When I press on the gas it goes off. I have not put a mechanic gauge on it yet. That I will try soon. My concern could it be bad main bearings? Has anyone had this problem? I use the standard oil Toyota recommends. This has only started in the past 1 month. Any thoughts would be appreciated.

vital22re

iTrader: (2)

get a mechanical guage and go from there. Could be a faulty sender.

mstasiewicz

Thanks, I did replace the sender and get the same problem. I will try the mechanical one.
Thanks

Ron Helmuth

update please? You got me curious...

mstasiewicz

Hi, I finally got a mechanic gauge installed. At idle the gauge is down at 5 psi. I talked to a toyota tec and he told me the Oil sending unit goes on when the oil pressure gets down to 4.7 psi. He also said at Idle it should be around 15 psi. Well there you have it. So now I tested to see what the pressure would jump to at upper rpms. I pushed it up to a little over 3K rpm and it never got over 12 psi at running temperature. The toyota tech told me if it does not have the pressure it is a serious mechanic problem. More then likely bearings have gone and leak the pressure around them. So it looks like a lower end over haul. Oh Joy.

Animas

Can you give an update? We have a similar issue on a 2000. We have replaced sending unit twice. When pressure is tested it is at 25 psi. Seems fine, but oil light will not go out. No noise in engine. Oil level on dipstick good, changed oil, used synthetic. If we put in mechanical gauge, should we be set? I've read about looking at the oil pan, pump etc. How far should we take this?

mstasiewicz

HI, my mechanical gauge showed when the oil was cold about 45 psi. Then when warmed up to operating temp it was below the 5 psi at idle. If you raced the engine while warm the oil pressure would only go to 15 psi. I pulled the engine and found bearing #3 bearing totally warn out and the oil was leaking from around it. It was so bad that small parts of the bearing broke off, traveled through the oil stream got stuck in the heads and carved grooves in the bearing races of the cams. As the heads are all aluminum as are the cam races, the cams are steel so now I have a set of heads probably not worth anything. Now one thing to note, is that this engine when I got it had a TRD supercharger on it. I removed it about 4 years ago. So superchargers put a low of wear and tear on the main bearings. Is your engine supercharged?

mstasiewicz

Also, how did you get a test of 25 psi? Was that using a mechanical gauge? Can you give me all the operating parameters when you got the 25psi? The oil light comes on only when the system reads below 4.7 psi oil pressure in the engine.

Animas

After we did one sending unit and an oil change, with higher viscosity light was still on. We brought to our technician. The Tech ran for 30 minutes at idle to even get the light to come on, at that point we were told psi was 25, mechanical gauge. So he pulled the aftermarket sending unit (second unit we had installed) and put in an OEM. Ran for another 30 minutes, no light. We picked up vehicle, drove 10 minutes home, light came back on. We now get the light after 10 - 20 minutes after driving. The engine is not supercharged. We are adding manual gauge and looking at working on the oil pan and eventually the pump. I'll try to get other details for the 25 psi. This is not a supercharged. We did replace a few cylinders about 4 months back after a misfire code.
Got in there with a manual guage, after warms up hits below 5 psi. If we turn the truck off and restart, pressure comes back to normal. We are going after the oil pan, hopefully find it there. Thanks.

Animas

Well a week later, we finally got the oil pan off, found debris and a plugged passage, good news. We decided to see if we could take a look at the bearings. Took more time that we thought, but the bearings look good. Back together, pressure is good and light is off! Wished we didn't mess around with the sending unit - should have gone straight to the manaual gauge.