4age 16v Oil Pressure drop while under very light load

[haydenz]

CAR - ae86

MOTOR - 4age JDM 16v (running oil cooler with remote filter)

USE - Daily

PROBLEM/QUESTION - On engine startup oil pressure is fine on idle no issues. When driving the car the oil pressure drops drematically towards low. This only happens when the car is cruising (light acceleration load). Under accel a heavier load it rises again back to normal, and once idling, pressure remains normal. No knocking or oil leaks occur when driving and pressure seems to be at its lowest point.

OCCURS/STARTED WHEN - I had not driven the car in a while, and noticed it the last time I drove it.

I havent driven the car since......any help would be great!

Thanks

[pen15]

well imo there is one of 3 things

1. you have somehow crushed a bearing but its hanging on im thinking a main bearing the center one this could have occurred as with an oil cooler and remote filter it takes some time to build oil pressure in the lines and cooler if the motor has been sitting for a while it drains back down if this is so if you have started it and a bearing has picked up on the crank loosing clearance i have seen this before if the motor needs a rev to keep it running

2. the sensor you are using is faulty or there is an issue surrounding the sensor try using another oil pressure sensor and try when in neutral in the garage

3. the oil pressure relief vale spring has broken and at idle there isnt enough pressure to open it relieving the pressure to bypass but at low loads it is enough pressure to bypass oil but with more load comes enough pressure to bypass and lift the total oil pressure can you give me an idea on what sort of pressure you have at idle and when the problem occurs in more detail rpm range and psi pressure

cheers
mat

[t-nol]

Bearing problem. Mine had the same syptoms, kept driving, spun big end bearings. Get it out and fix it early, will save you money.

[Slimer86]

What oil pressure gauge are you using? Stock?
If stock, borrow/buy an aftermarket gauge to clarify that what the stock gauge is telling you is the truth.

Why pull the bottom end to pieces if its unneccessary. Get a little more supporting evidence before coming to false conclusions.
Check the symptoms, then follow back to the root cause.
Something else leads to big end bearing to failure.

[Matt]

Better to replace the bearings than ruin the crank.