Oil pressure in rb20det

[sammus]

Hi guys,

My oil pressure is suddenly way lower than it should be.

Previously, if i'd turn it on, the oil pump would pump it straight up and the oil pressure guage would read 4.

Now, however there's problems. The engine starts, oil pressure comes up to 4, but then drops way down after a few minutes. It idles at less than 1 on the guage, and when reved it doesn't come up to more than 2.

Any help as to the reasons much appreciated... Sam

hoping it's not the oil pump.

ps. i noticed the problem after just getting onto sandown, turned it straight off and got a towtruck home to be safe lousy day that was.

[blackr32gtst]

hey mate not here to help as i have the same problem

but i still drive mine every day and it is fine but to be safe i would like to no so i can fix problem also

[predator]

same problem.. I've taken mine on the track, given it many cainings in the mountains, and its all fine. Wouldn't worry *too* much.

[MerlinTheHapyPig]

that's normal afaik. mine reads 4 cold idle, but driving normally sits at around 1.5-2ish and sits really low when stopped at lights. i've been told higher than 2 is bad once the car is warm.

there is a red light that comes on which is the oil pressure warning light (it comes on when u start car for a second or two). i figure if that light's not on, all good!

also the stock oil pressure sender & gauge is crap, so go aftermarket if you want to keep a better track of oil pressures.

[[HOTNXR]]

from what i remember, the slower the presure the more time the oil has to cool down... so i think its fine...

[sammus]

thanks for the replies lads. after researching, i'm pretty sure it's to do with the second number in the oil i'm running. i'm using 5w-30 ... if i were running an oil with the second number as 50, ie. higher viscosity at higher temp, it just might fix the problem. but seeing as the problem isn't really much of a problem, i'll leave it till next time.

oh and also... i think the reason this happened months after the oil had been changed was because the oil's molecules got broken down over time making it thinner when the engine was up to it's running temperature :bananaman

[Beer Baron]

the nissan specified grade of oil is 7.5W30 so going to a *W50 is only going to 'mask' any problem (if there is one). I wouldn't go thicker than a 10W40.

ok, oil pressure around 1 bar at idle is no big problem but when driving along at say 3000rpm you should have pretty good pressure then. do you?

Otherwise it could be a faulty gauge.

[sammus]

indeed, i wouldn't put in 50 because it wouldn't get around the engine quick enough. the pressure guage does not necessarily correspond with oil flow either.

at 3000rpm i believe it was a bit under 2. it was just the idle pressure that worried me. next time i'll be using the nissan 7.5w-30.

[Beer Baron]

yeah the nissan semi synthetic is not too bad. it's quite cheap but I would say it's fine for a stock/near stock car. dunno if i'd use it on the track though as it's film strength and high temp lubrication would not be as good as some of the higher priced stuff.

hmm, 2 bar at 3000 is a *bit* of a worry I would have thought 3+. i mean it is an RB20 so whats the worst that can happen? very cheap to replace. on the other hand if it is the original (un-rebuilt) motor then that is probably about right. on my RB26 (fairly recently rebuilt motor) the oil pressure when hot is well about 4bar at 3000rpm (off the top of my head) any lower than 3 bar and i wouldn't feel so good. it's an RB26 though...

[Richo]

that's normal afaik.   mine reads 4 cold idle, but driving normally sits at around 1.5-2ish and sits really low when stopped at lights.   i've been told higher than 2 is bad once the car is warm.

Well I've been told that a low oil pressure at iddle when warm is indication of an old engine say 150Ks -200Ks, also that in a tight well preserved engine it should sit on 4 at idle when warm. :confused:

Mine sits at 3 or a bit lower than, when warm at idle, but when cold in the mornings it just jumps up to 8 for a good couple of mins, and gradually goes down as the engine warms up.

[foznice]

I was thinking about this after I finished talking to you Sam and I was looking at pictures of my car. In this picture the car's idling but it looks the oil pressure guage is reading zero. I could be in the same boat as you guys.

[xRHETTx]

Im pretty sure the recommended oil pressures are in the engine manual?

When the car is cold it should read high at about 4 or so, but as the car heats up (and the oil heats up too and becomes less viscous) the pressure should drop again.

About 1 at idle, 2 at 1000rpm, 4 at 4000 rpm is normal i think?

[MerlinTheHapyPig]

i think before you start wondering what's wrong with your engine, get an aftermarket oil pressure gauge & sender, just to make sure it's not the stock sender which is providing inaccurate readings.

(actually, after driving the car this morning and paying more attention to the gauge, i'll revise what i said before. when warm driving at constant speed, it's usually on around 2.5-3ish.)

[sammus]

yeah we've been doing it against what's in the manual. we put new oil in today... thicker oil. on the first drive it was slightly better... but after a longer while it was much better and back to how it was before. happy days for now. we went to repco planning on getting 0w-40... ended up getting mobil 1 5w-50

[MerlinTheHapyPig]

hmm, might try mobil 1 next time, slightly thicker. im using 10w40 at the moment.

[sammus]

well... most of the time since the change it's been fine, but once so far the pressure has dropped down to almost zero. so i let it sit there for a while watching it, drove off and it jumps up again and next idle it didn't drop back down. maybe the sending unit. we all have the same cars, same ages, same rate of failure.

next time it happens we'll tap the sending unit with a wrench and see what the guage reads

[Drifterdan]

Yeah mine does this too with no obvious problems.

[xRHETTx]

Oil pressure: Sender failure

Like all normal vehicles, good oil pressure is essential. The sender itself is located by the oil

filter on the left hand side of the block.

The following figures are the workshop manual specification for oil pressure on the

RB20DET...

1kg/cm2 @ 600 rpm

3kg/cm2 @ 2000 rpm

4kg/cm2 @ 6000 rpm

My own car has a oil pressure gauge that doesn't behave due to a fault somewhere, so I had a

check done by running a remote gauge which gave the correct numbers... Whew! Update: the

oil pressure switch replaced.

Thats from the The Sky is the Limit skyline book thats floating around www.skylinesdownunder.com and sau somewhere

[sanger]

hey mate another thing that you can have problems with is the oil pressure sender unit. When my car came over from japan it was fine then after about 3 weeks i noticed while i was driving that the pressure dropped to zero, Now if this happened it would have been game over for the engine so i knew the gauge reading was full of shit. I had the gauge tested an it was fine so we ended up tracing it back to a faulty sender unit... Another thing that can also happen i that the gears in the oil pump wear out which is much more costy to fix as you have to remove the sump etc to fit a new pump.

[Bazelinez]

This comes up so often. Its pretty much guaranteed that MOST r32 oil pressure senders are up shit creek.

Mine works intermittently, sometimes sitting on 0 for half an hour, other times going up past 4.

Its basically a case of the light, if it comes on kill the motor! That is the most important part. The proof lies in the fact that after 7 months on the road my car has read zero sometimes and its still going strong.