What are the signs of oil pump issue on RB26?

[judasentinel]

What are the different signs that hint at an oil pump/drive issue with an RB26? And how does one diagnose it?

What I am observing in my recently installed RB26DETT in my GTS is that on cold start, the stock oil pressure gauge is showing the pressure to be at the '4' (halfway) mark. Then it slowly drops to the quarter (2) mark between 0 and 4. After warming up and driving it for a bit, it moves close to zero, and sometimes drops to zero. When I rev the engine, it goes back up to around the quarter mark (2). And after driving it hard, the pressure seems to stay between 0 and 2, with the needle moving up very slowly when I rev it. I am worried and having no experience with RB26s, I dont know what to make of it.

Is this a sign of an oil pump failure? The oil level is fairly consistent as per the dipstick. As far as I know, there are two oil pressure sensors on an RB26. I am using RB25 oil pressure sensor at one of the locations, under the intake manifold.

How do I confirm what could be causing it? Could leaning out cause a drop in oil pressure when engine is hot? My engine temp gauge stays at where it should be, which is a little above the halfway mark.

What are the visible and obvious signs of oil pump failure or the drive giving up? Can you change the oil pump or the pump drive without pulling the motor out?

Any help would be appreciated.

[assass1n]

if you're still using the stock oil pressure sensor. it is very very unreliable. at least on a stock gtr.

[falcon]

I would never trust the stock oil pressure gauge.

An aftermarket oil pressure gauge is basically my #1 recommended gauge to buy first.

That, and boost if you're running over stock.



And when your pump fails, trust me you'll know

Keep in mind too that a stock engine runs about 1.8-2.0bar at idle. I don't know what that relates to on the stock gauge, but it will be very low on the needle.

[FITZY_07]

Munib, I think PH_motorsports had this same issue. Turns out it was just the sensor/gauge, not too reliable....

[PH_Motorsports]

got an brand new autometer oil pressure gauge available cheap and brand new oem oil pres sensor

pm if you want any

[Terrh]

for starters

DON'T DRIVE THE CAR UNTIL YOU FIGURE THIS OUT.




my GTR acted similarly when I bought it. Ran fine, no noises, etc. But not much oil pressure when hot, sometimes none. and then it blew up, #2 conrod bearing failed.




Get a real oil pressure gauge. Install it. See the real picture of what's going on.

The stock gauge is simply not trustworthy. There may be nothing at all wrong with your motor OR it could be accurate and has big issues. You'll never know until it's too late.

Anything below 15psi@2000rpm = serious issues inside. And it really should be more than double that. Any drops to 0 or very near 0 = problems.

Without taking the motor apart it's impossible to know why your oil pressure is dropping, it could be something as simple as the wrong grade of oil or a bad oil pump, or it could be serious bearing wear, an oil squirter bolt backed out and is laying the pan now, etc.

[tokes]

It's possible to change the oil pump in the car (according to tyndago) but much easier with the motor pulled.

You cannot fix the oil drive issue with the motor in the car. The crank needs to be removed and have the old drive machined down, and then have the new collar press-fit on.

[specialedition]

My GTR had the same problem, The Gauges are not very realiable.

[judasentinel]

It starts at around 56 psi (4 on the stock gauge), idles at 25-28 psi (2 on the stock gauge) after warming up, but once driven a bit hard, it drops to close to zero, or stays at around 15-18 psi thereafter (between 0 and the first line).

Could it be caused by the inability of the oil pickup tube to pick the oil up effectively?

[Terrh]

you're still using the stock gauge though

those readings are useless.

[GTR-Dad]

It starts at around 56 psi (4 on the stock gauge), idles at 25-28 psi (2 on the stock gauge) after warming up, but once driven a bit hard, it drops to close to zero, or stays at around 15-18 psi thereafter (between 0 and the first line).

Could it be caused by the inability of the oil pickup tube to pick the oil up effectively?

Not likely. If the pickup is sucking air, oil pressure will drop out rapidly. It sounds like yours is a gradual drop off as things warm up.

As posted earlier, there could be a few causes of low oil pressure. Think of oil pressure as a backpressure resulting from flow of a viscous fluid through a network having a resistance to flow. Variables controlling backpressure are flow rate, fluid viscosity, and circuit resistance.

Pump drive failure is sudden and catestrophic. High rpm and/or bouncing off the hard limiter are often trigger events.

If your pump is wearing out and internal clearances are getting bigger, you'll see greater internal leakage and substantially less flow with warmer, lower viscosity oil. This can result in low pressure at idle.

Circuit resistance reduction by one of the faults Terrh describes could also cause your symptoms.

Unless you're pumping oil in huge quantities, you should expect to see lower oil pressure at idle. The problem criteria Terrh offers of P<15 psi @ 2000 rpm and near zero at idle fits well with my 'feel' for the process.

If you discover that oil pressure is problematically low you'll need to decide if you want to fix it now, which probably involves pulling the engine and tearing it down, or fix it when the car schedules the repair. If you go for the second option, you may be able to delay failure by running heavier oil. This will increase flow if the pump is the problem and increase pressure available to key lube locations if circuit resistance is compromised.

GL

Dan

[Nismo BKK]

Not likely. If the pickup is sucking air, oil pressure will drop out rapidly. It sounds like yours is a gradual drop off as things warm up.

As posted earlier, there could be a few causes of low oil pressure. Think of oil pressure as a backpressure resulting from flow of a viscous fluid through a network having a resistance to flow. Variables controlling backpressure are flow rate, fluid viscosity, and circuit resistance.

Pump drive failure is sudden and catestrophic. High rpm and/or bouncing off the hard limiter are often trigger events.

If your pump is wearing out and internal clearances are getting bigger, you'll see greater internal leakage and substantially less flow with warmer, lower viscosity oil. This can result in low pressure at idle.

Circuit resistance reduction by one of the faults Terrh describes could also cause your symptoms.

Unless you're pumping oil in huge quantities, you should expect to see lower oil pressure at idle. The problem criteria Terrh offers of P<15 psi @ 2000 rpm and near zero at idle fits well with my 'feel' for the process.

If you discover that oil pressure is problematically low you'll need to decide if you want to fix it now, which probably involves pulling the engine and tearing it down, or fix it when the car schedules the repair. If you go for the second option, you may be able to delay failure by running heavier oil. This will increase flow if the pump is the problem and increase pressure available to key lube locations if circuit resistance is compromised.

GL

Dan

Well said....

For sure, using the stock oil pressure gauge for reference isn't a good idea and getting either a new sender or a/m gauge to get a more accurate indication of the oil pressure before jumping into conclusions.

[mwracing]

I would never trust the stock oil pressure gauge.

An aftermarket oil pressure gauge is basically my #1 recommended gauge to buy first.

That, and boost if you're running over stock.



And when your pump fails, trust me you'll know

Keep in mind too that a stock engine runs about 1.8-2.0bar at idle. I don't know what that relates to on the stock gauge, but it will be very low on the needle.

X2...

[gtrtt]

The stock oil pressure guage should be ignored until you get something accurate. All it does is cause undue stress. I refrained from using 5th gear for a week due to it reading zero or just above when cruising at 110 km/hr. yet the damned thing reads 2/3 or higher on startup.I've got HKS 60 mm guages and dash pod that came with the car that I'll be selling as they don't have the sensors connected and the first new guage going in on the pillar will be a oil pressure. I'm curious to see what your pressures end up being, Judas. Post it up when you've installed.


Nick

[owennh]

I would never trust the stock oil pressure gauge.

An aftermarket oil pressure gauge is basically my #1 recommended gauge to buy first.

That, and boost if you're running over stock.



And when your pump fails, trust me you'll know

Keep in mind too that a stock engine runs about 1.8-2.0bar at idle. I don't know what that relates to on the stock gauge, but it will be very low on the needle.

+1 Stock sending unit is a peice of **** , toss it. With new senders I get approx 2 bar at 2000 rpm with both my cars.