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09 ZD30 CRD Wagon
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After doing a load of engine work, the big girl is running better than ever. I also put in an oil pressure gauge to keep an eye on things. after a few weekend trips here’s what I’m seeing.

Once fully warmed up, she sits at 11-13psi at idle.
At 100km/h, it’s about 30-33psi.

I’ve set my low pressure alarm to 10psi and it hasn’t gone off at all yet.

All good for the CRD?
 

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09 ZD30 CRD Wagon
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Discussion Starter #2
Found in the 2007 supplement of the ESM....
This is really concerning. States 28psi at idle, and 57psi at 2000rpm.

Considering i'm as low as 11psi at idle and about 30psi at 2000rpm, I'm very concerned.

However, my oil pressure warning light on the dash has never come on... strange

517093
 

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2010 GU DX CRD Grenade :)
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What brand gauge have you got? Just out of interest as I have found the same thing with mine, I have a cheapo saas autoline gauge on mine.

I do have a saas muscle series gauge on my d22 yd25 and that reads about the same as what the factory specs say it should, so I'm assuming that either the sender unit on the Patrol is poor quality or just the gauge altogether... The pressures when cold and during warm up look perfect, but once at temp I'm getting about the same as you.

From what I've read the low pressure switch should illuminate the warning light at 15psi, so I'm trusting the engine to have more than that...
 

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Not sure if that's directed at me or the op, but I'm not sure about mine. The oil was changed just before I bought it and they didn't tell me what they used. I will be doing a change soon, trying to decide what to use though...
Maybe rx super?
 

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GUII ZD30DI Wgn
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That should be fine. TBH I recon that any 15W40 is OK as long as you change it often enough. I've noticed some blokes are running 10W40 synthetics and IMO it is too thin for our engines.
Fully agree, 15w40 fo me and no full synthetics.
 

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That was my thoughts too, either rx or gulf western top dog xdo... I know oils is another whole can of worms though haha
 

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That should be fine. TBH I recon that any 15W40 is OK as long as you change it often enough. I've noticed some blokes are running 10W40 synthetics and IMO it is too thin for our engines.
Not sure I get the too thin thing. With oil viscosity ratings, the first number with W (winter) is the cold pour point and only relates to cold temperature start up viscosity, so yes at cold temperature 10W is less viscous than 15W.

However, the second number is what really matters for operating temperature. It is the viscosity and sheer strength at full operating temperature measured at 100C. So at temp, the 10W40 and 15W40 are effectively the same. It's only the start up temperature that's different.
 

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After doing a load of engine work, the big girl is running better than ever. I also put in an oil pressure gauge to keep an eye on things. after a few weekend trips here’s what I’m seeing.

Once fully warmed up, she sits at 11-13psi at idle.
At 100km/h, it’s about 30-33psi.

I’ve set my low pressure alarm to 10psi and it hasn’t gone off at all yet.

All good for the CRD?

Mine is a Di, but I have the exact same thing. Rebuilt motor, oil pump tested and within spec. At start up I get oil pressure coming up pretty quickly to 85 or 90 then slowly drops to about 20 as it warms up. Once at full operating temperature, oil pressure is a bit lower than what you have posted in that page above.

At full temp when I slow down to idle, at first pressure is 20 to 25, but as it sits longer at idle the pressure drops to just above 10. Accuracy of the gauge or the markings anyway are a bit hard to judge at that low pressure. But the oil light doesn't come on.

The more I read about this, it seems pretty common to notice after fitting an oil pressure gauge to both Di and CRD. My gauge is fitted to the left side where the low pressure switch for the light is. Looking at the oil flow diagram it should be the same pressure as at the other side where Nissan suggest to take oil pressure readings.

I was concerned about the low pressure and if it was oil related. During the hottest days of Summer I decided to change oil to see if that was the issue. I changed to 15W60 just for a hot conditions test on the beach. After some hard sand driving and oil pressure was behaving well. I still find pressure at idle after a few minutes drops down to around 10psi.

So it has me stuffed if it is a problem with the oil pump or not.
 

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Here's another thread about it as well.
This gives a hint that the issue might be to do with the oil cooler and either the pressure bypass valve or pressure maintaining valve near the filter. Possibly one of the two valves is sticking, leaking or bypassing at the wrong pressure.

 

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Good stuff Geordie, thanks for those threads. From reading that, I'm going to assume there are a lot of patrols getting around with apparent low oil pressure, without knowing as they have never been tested or had gauges fitted. It would be interesting to get a mechanical gauge on to double check I guess, my sending unit is fitted to the block near the starter motor on my crd, with a t piece to keep the factory sender.
 

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GUII ZD30DI Wgn
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Are you sure your gauge is reading correctly,? Had a look back through the thread and can't see verification on this.
 

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Are you sure your gauge is reading correctly,? Had a look back through the thread and can't see verification on this.
I'm not entirely certain mine is, but after reading another one of those threads linked where someone with a redarc gauge is getting about the same readings as I am, makes me feel a bit better... Then again, I guess there's nothing to say that is correct either.

With the service manual saying that the low pressure switch displays the light "when close to 0 oil pressure" makes you wonder how close to 0. It also makes you wonder how accurate the "pressure sensor" that the later models have on the block near the starter motor is. I don't know whether this goes on voltage or pwm signals to the ecu, but I have no way of testing it. According to the snippets from the manual, that should put the light on if the values don't match what the ecu is looking for.
 

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I'm not entirely certain mine is, but after reading another one of those threads linked where someone with a redarc gauge is getting about the same readings as I am, makes me feel a bit better... Then again, I guess there's nothing to say that is correct either.

With the service manual saying that the low pressure switch displays the light "when close to 0 oil pressure" makes you wonder how close to 0. It also makes you wonder how accurate the "pressure sensor" that the later models have on the block near the starter motor is. I don't know whether this goes on voltage or pwm signals to the ecu, but I have no way of testing it. According to the snippets from the manual, that should put the light on if the values don't match what the ecu is looking for.
That is the only one my old DI has, it doesn't have the one in the oil cooler.
 

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Hmm. It had me concerned at first that oil was the issue or possibly diesel leak dilution of the oil. But after testing with fresh oil and much higher viscosity, still have the same thing after idling for a minute when at full operating temperature.

I have two areas to further investigate, first like geeyoutoo said, could be accuracy of the gauge particularly right down at the low end of its range. Mine is however, a new Autometer electronic gauge. They are meant to be very accurate, so I'm leaning to thinking that it's not the gauge, but might see if I can rig up a test gauge to confirm.

Second thing is the function of the oil cooler bypass valve and the filter pressure valve. I really don't fully understand what and when they each operate. But given the pressure can build to 100 on cold start, I guess they shouldn't be dropping the idle pressure unless one valve is leaking.

Last thing not so much a concern but an observation of the oil press light and low press light switch. I did test it out of the car with a small pressure gauge and hand pump. The light is on to start with 0 pressure, then as I increased pressure, it would go off at about 14 psi. Then I dropped pressure slowly but couldn't really accurately control it but the light came on again somewhere below 10 and before 0 on my gauge. Need to try that again and test the Autometer electronic gauge at the same time if I can rig something up.
 

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That is the only one my old DI has, it doesn't have the one in the oil cooler.
Is the one on yours a switch or a sensor in that location?
Hmm. It had me concerned at first that oil was the issue or possibly diesel leak dilution of the oil. But after testing with fresh oil and much higher viscosity, still have the same thing after idling for a minute when at full operating temperature.

I have two areas to further investigate, first like geeyoutoo said, could be accuracy of the gauge particularly right down at the low end of its range. Mine is however, a new Autometer electronic gauge. They are meant to be very accurate, so I'm leaning to thinking that it's not the gauge, but might see if I can rig up a test gauge to confirm.

Second thing is the function of the oil cooler bypass valve and the filter pressure valve. I really don't fully understand what and when they each operate. But given the pressure can build to 100 on cold start, I guess they shouldn't be dropping the idle pressure unless one valve is leaking.

Last thing not so much a concern but an observation of the oil press light and low press light switch. I did test it out of the car with a small pressure gauge and hand pump. The light is on to start with 0 pressure, then as I increased pressure, it would go off at about 14 psi. Then I dropped pressure slowly but couldn't really accurately control it but the light came on again somewhere below 10 and before 0 on my gauge. Need to try that again and test the Autometer electronic gauge at the same time if I can rig something up.
Hmm, I'd agree that autometer are generally pretty accurate and if you're getting the same readings that I'm getting on a saas gauge, it makes me wonder if it is a common thing.

I'm sort of subscribing to the old school train of thought that I've read about of 20psi pressure for every 1000rpm. I can't recall when I saw it, but I was having a good look on my gauge on the way home from work today and it is pretty much that. With the fast idle switch on, the pressure sits on just over 20psi. At roughly 2000rpm on the tacho is pretty much spot on 40psi on the gauge...

The 10psi at low idle isn't looking fantastic, but seems to be a regular pattern, on here at least...
 
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