GroundControl

ok, this may end up being a long story...

i have been attempting to resolve this issue by searching various threads here but now i have become lost in all the information. to avoid going down the wrong rabbit hole i am asking for the local experts opinions on this one. so here it goes

I recently had the clutch replaced on my 1990 4runner (22re 4wd 5spd)
the mechanic recommended that i also replace the oil pan seal since it was leaking, and "it is much easier to get the pan out with the transmission already out".
$750 for the clutch replacement and $200 for the oil pan seal and i was good to go. everything seemed just fine until...

the next weekend i drove it from phoenix to wolf creek colorado. on the way home while driving through the northeast part of arizona i had a problem. i looked at the gauges and the oil pressure seemed low, it was getting even lower until the needle basically fell to zero.

I immediately pulled over, checked for leaks, checked the dipstick. everything was normal. i started her up and the pressure came back. we drove for another 10mi or so and the pressure gauge started to show low again, then it fell to zero. i limped into Kayenta to stop for gas driving like a grandma.

i topped it off with an extra half quart of 10-40 and then drove the rest of the way home (250mi) watching the gauge like a hawk. it seemed to be low (just at the left of image of the oiling can) the rest of the way home, but no fatal drops to zero.

what does this sound like to you?

i have more info but this is getting long so i will wait for replies. please help, i need my ski-mobile this winter!

wyoming9

iTrader: (1)

I would make a guess either a bad connection at the sending unit but from what you said it worked good for awhile then went low sounds like a bad sending unit.

I would replace that while I had the old one out I would put a mechanical gauge on just for piece of mind and make sure you have good pressure.

The fact that you didn`t spin a bearing on the way home leads me to think sending unit.

Good luck in any case

GroundControl

Wyoming9,
Thanks for the Reply, I am inclined to think that the sending unit is OK because It was replaced about 10-15k miles ago. When it went bad that time it basically died completely and suddenly, the gauge permanently read zero. I had it replaced at the dealership and they put on a brand new factory Sending unit... problem solved.

Also, when watching the gauge during various stages of driving, rpms, etc. the gauge acts normally reading proportionally to the RPM. But after cruising for a long time the pressure steadily gets lower until it is just marginally higher than it would be at idle (see pic for idle pressure)

This pic shows the oil pressure during Idle, the needle is right at the first marker line.


Is this normal Idle pressure for everyone? what is it normally at when you have been driving for long enough to reach full Temps...

the more input I have the better I can judge my gauge readings, Is it worth my time to install a mechanical gauge? I saw the many threads about aftermarket gauge installs. If I can find the right fittings I want to put a mech gauge in while still running with the factory Sending Unit so I can compare readings side by side...



by the way; I took it to the dealer only because I was also geting the Factory Recall done on the Steering Linkage.

wyoming9

iTrader: (1)

What happens is the oil gets past the seal in the sending unit not allowing it to move as far as it should.

Shut down engine oil gets drawn out from where it was then works normal till enough oil is on the other side again.

No big deal to get the correct fittings to put in a tee so you can run both the factory and a mechanical gauge.

Then again the oil weight and temperature and if you have been slacking in the oil change intervals might be a cause but I really doubt it

GroundControl

I finished installing a Mechanical Gauge just in time to have it during my recent drive to go skiing again, the round trip to ShowLow, AZ was about 500mi total. Not once did the Oil Pressure drop to Zero like it had on the previous two trips to colorado. However, I was able to compare the reading from the sending unit/ cluster gauge to an actual PSI value during cruising conditions... I was able to put my worst fears to rest since the lowest oil pressure I experienced during cruise was about 45psi.

Here are some pictures that show the readings during various RPM's.



Unfortunately this does not help me explain the sudden loss of oil pressure that had me so worked up in the first place. I also still have a suspicion that the oil pickup tube is letting air bubbles into the oil pump. more to come on that investigation...