Dropping Oil Pressure - Yes I know.....

Hi,
I fitted an engine oil pressure gauge to my 2003 GU 3.0 litre Patrol.
I use Penrite 5W50 oil, changed every 5000km.
Recently on longer (warmer) trips the oil pressure drops as follows:
a. 2500RPM: 80 PSI drops over time (an hour) down to 60PSI
b. 2000RPM: 65PSI drops over time down to 40PSI
c. after an hour highway driving on taking foot off accelerator, drops to idle and pressure drops down to 10PSI maybe less, sets off my low pressure alarm.

My mechanic reckons it is an oil viscosity issue, so we increased it to 10W50, made no difference last trip out.
He gave it a Wynn's engine flush and changed oil to 15W50 per Nissan Manual.
He bolted in a pressure gauge and said at 20 on mine is 27, so likely all ok....
BUT....why does it drop about 15PSI while driving over time...??
Is it just oil viscosity, or..has someone else seen similar??
Any help, ideas ........ Thanks.

Let me guess you have the Redarc oil pressure gauge? I fitted one and mine also did the exact same thing until the gauge finally died and wont read oil pressure at all. If the OEM oil light isn't coming on then I would say is the gauge, as I believe the OEM senders are switched at 10psi for the light to come on the dash.

Thanks Mudski.
I was coming around to that idea too, but...was worried about it being a real problem with my truck.
As of now, will reset my alarm to lower, and watch the pressure go up and down, and hope, expect it is getting thru the engine correctly.
And will use the NISSAN Pressure switch to tell me if anything is actually wrong..
My gauge only a year old. Might call them to see what can be done...

Mudski?? Your pressure dropped as you were driving too? ..and then just died??
I thought it was all things like Main bearing wear, or those terrible engine death things.
It still goes up and down as i accelerate...just at lower pressures...
If it is the same, then was it gauge, or sender? No replies from REDARC for past week.
Might go say hello at the 4WD show and ask them...that might get thier attention...

As I mentioned a few days ago in another thread my workmates redarc gauges died in a similar fashion. His egt gauge went sky high and he shit bricks but it was a faulty gauge or the sender unit.

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GU's have iffy sender units my oil light used to come on, I'd pull over check the dip stick all good,
restart the motor and the light would go out.
You'll need to match the sender ohms to the gauge wouldnt you

Threedogs,
The gauge sender is in a T-piece with the Nissan switch. The sender and gauge came together, so hope, assume they are matched..

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Originally Posted by AJTich

Mudski?? Your pressure dropped as you were driving too? ..and then just died??
I thought it was all things like Main bearing wear, or those terrible engine death things.
It still goes up and down as i accelerate...just at lower pressures...
If it is the same, then was it gauge, or sender? No replies from REDARC for past week.
Might go say hello at the 4WD show and ask them...that might get thier attention...

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Yes it dropped whilst driving then just died to the point where its doesn't work at all. So your is a Redarc too?

yep.. bugger.

Ok I just spoke with Redarc. I have two options.
1. To test the sender unit with a multimeter to see if I get any voltage change in the sender unit. If theres no voltage the sender is no good. And they will replace it.
or 2. Remove the gauge and sender and send it back for them to test.
Now I just need my car back so I can test it. Lol.

At least living in Adelaide, so easier to get to them..pain to get out of truck though. Might ask them for a replacement sender for mine...

Thanks Hodgey, Will ask the REDARC guy at the Show on the weekend...see how to get a replacemetn sender.

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Originally Posted by AJTich

At least living in Adelaide, so easier to get to them..pain to get out of truck though. Might ask them for a replacement sender for mine...

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I spoke with Matthew at Redarc. So if you ring them, ask for Matthew. He's got my our conversation we had on file....
With any luck i get my car back tomorrow. And i will test the sender unit tomorrow...

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Hey Hodgey, yes it is scary...
Today my EGT/Boost gauge Boost went to MAX..but after a little while came back to reading correctly.
Starting to wonder about the previous mechanic who fitted them and do i need to redo the whole loom to close that out.

I havent tested my sender unit yet. But i had a look at it and its wet with oil where the wires come out. So im assuming its fubar. If i have time tomorrow i will remove the gauge and run a dmm on the sender wires to see if theres voltage.

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Just thought I'd touch up on this topic again. I have tested my sender unit and there is no voltage change at all when the car is started. So I guess the sender is fubar. Time to ring Redarc.

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Originally Posted by mudski

Just thought I'd touch up on this topic again. I have tested my sender unit and there is no voltage change at all when the car is started. So I guess the sender is fubar. Time to ring Redarc.

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I dis the reset all on the gauge, changed oil to 15w and did an engine oil flush at same timw and ao far seema to hold 》25 when warm. Bloody gauges...

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Originally Posted by AJTich

I dis the reset all on the gauge, changed oil to 15w and did an engine oil flush at same timw and ao far seema to hold 》25 when warm. Bloody gauges...

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Yeah i kinda wish i never had them (oil pressure and water temp). I keep on looking at them for no need. My water temps fluctuate a lot but the oem gauge doesn't move. I might even get rid of it and put a clock or something there. Lol.

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Quote:

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Originally Posted by mudski

Yeah i kinda wish i never had them (oil pressure and water temp). I keep on looking at them for no need. My water temps fluctuate a lot but the oem gauge doesn't move. I might even get rid of it and put a clock or something there. Lol.

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Water temp scared me because the Nissan one hides behind driver's arm...and had a temp rise climbing thru the Hysen Tunnels... So fitted that one...and figured oil pressure to keep oil level checked..

Quote:

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Originally Posted by AJTich

Water temp scared me because the Nissan one hides behind driver's arm...and had a temp rise climbing thru the Hysen Tunnels... So fitted that one...and figured oil pressure to keep oil level checked..

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Yeah im questioning the accuracy of the Redarc water temp gauge too. Ive seen it hit 110c on the Redarc gauge, yet the oem gauge doesn't go any higher. I know the oem gauge works though, as on our Dargo trip when we hit the black top on the way back from a day trip, it was a real long down hill run, it was bloody cold outside, both gauges dropped down.

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I see 90 when its hot...so that ia way better than 1/2 way all the time. I will certainly keep an eye on both.

Recieved my replacement oil, pressure switch last week from Redarc. Fitted and all is good for now. Although i do question its accuracy on oil pressure and water temp.

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I've gone through 2 oil pressure senders on my redarcs, about to order a 3rd. The sender must be a poor design to keep failing like they do.

Yep, now my sender unit is stuffed. Oh well, 4 years is better than most people seem to get. $105 is a shock to the hip pocket but.
Hmm, and until it failed, using the 10W40 kept oil pressure and reviewing gauge accuracy per my older posts, it stays around 70 when really hot, and on idle drops to 25-30 so seems to all be good.
Bloody REDARC..they know how to charge.