Should my Oil Pressure Gauge Sensor be replaced?

[Kippers]

I need some advice please… I have very little technical knowledge and rely on an approved Honda dealership group to look after my 2002 car, as they have done for my 12.5 years of ownership plus the year before that when my brother had the car so, they know it well and I trust them.

During an annual service, I was advised that the car had a slight oil leak and that at some stage I should get the oil gasket replaced, not urgent.
Some months later, the reading on the Oil Pressure gauge would sometimes dip to 1 or 2 whilst the engine was idling plus there was a slight smell of burnt oil coming from the outside vent behind the drivers door – nothing noticeable in the cabin nor was the car performance affected, the oil level on the dipstick was fine, no issue with the Low Oil Pressure Indicator light.

The oil gasket was then replaced and the Oil Pressure was stable for a few weeks, however, there was still some slight oil leakage (a few drops if car left on concrete for a few hours) and the smell remained. Then the Oil Pressure appeared to drop significantly, showing just above zero when idling, 2 or 3 when driving. Again, dipstick level fine, no issue with the Low Oil Pressure Indicator light.

The garage replaced the gasket again as they said that the first replacement may have been slightly damaged/crimped plus they changed an O ring.
Again, all fine for a few weeks, albeit there is still a very slight smell of oil occasionally (but, to be honest, I seem to have developed a habit of smelling the vents after any drive longer than 25 miles, not something I used to do!). Then this week the Oil Pressure Gauge again dipped to just above zero when idling after a 25+mile drive, 1 or 2 when driving. After shorter drives I haven’t noticed a problem.

The garage Master Technician has checked the ECU and feeds to the Low Oil Pressure Indicator light and has confirmed that everything appears to be working correctly, there is no problem with oil in the engine. He also obtained some sort of special tester that allowed the Gauge and the Sensor that feeds the Gauge to be tested and they appear to be fine too, however, at that time, the Gauge itself was quite happily showing a regular reading (4 or 5 I think) and didn’t seem to want to drop to zero as it was wont to do previously.

The garage therefore can not definitively prove what it causing the problem but have deduced that it may well be that the Sensor is temperamental as that seems to be the likely suspect. A new Sensor is £470. If it was £100, the Service Manager and I agree that it should be replaced, but at £500 neither of us are convinced so I thought I would ask for advice!

Searching the Forum I found this thread which seemed to suggest that I should probably just ignore the gauge reading …
http://www.nsxcb.co.uk/showthread.php?13878-Oil-Pressure-Reading-on-Gauge-What-s-Normal&highlight=oil+pressure

Should I get the Sensor replaced, or is there possibly another solution/diagnosis, or did I read the thread above correctly and I should just ignore the problem? Again, at no point has the Low Oil Pressure Indicator light flickered or come on when the engine is running and the dipstick reading is fine.

Many thanks in anticipation and sorry for the length of this post,
K

[goldnsx]

Searching the Forum I found this thread which seemed to suggest that I should probably just ignore the gauge reading …
http://www.nsxcb.co.uk/showthread.ph...t=oil+pressure

this.

Common failure after 15 years, just the sensor reading, nothing to do with the oil pressure in the engine, the sensor is just reading low. Ignore it or replace it. I was not patient and replaced it with a new one ($280 or so).

[britlude]

the oil gauge sensor is at the top of the engine after everything has had oil fed to it.

the oil pressure warning light uses a sensor much closer to the oil pump and is completely separate.

the oil pressure sensor is much like a old fashioned petrol gauge mechanism, and does get 'tired'. sos offer a replacement using another manufacturers 'tweaked' sensor and remote mount, tho whether it improves the gauge reading is subject to various threads on NSXprime

[Kaz-kzukNA1]

Hi, Kippers.

I won't go too much into detail but even with the fresh engine oil, when you remove the pressure sender unit (the ancient device that moves the needle of the oil pressure gauge), the oil inside the sender unit and the passage leading to it are much darker colour than the oil inside the sump.

This is due to the position of the sender unit within the entire oil distribution route, the sender internal design, how it is mounted to the cyl head and how the oil passage is routed inside the eng block plus what happens while the car is parked especially if you don't drive regularly.


You won't be able to keep monitoring the gauge while you are driving but if you take video, from time to time, you will notice random and inconsistent pressure reading on the gauge on some of the NSX even when you think you have no problem.




Please take a look at this video. This is from one of the NSX that I looked at and seen the same on many NSX.

This was taken while warming up the engine and you will notice that it started with around 4kgf/cm2 and then suddenly, dropped to 2.5 and then to almost 2.0 despite the engine rpm didn't change much during this period.

If you can keep watching the video till the end, the engine is still warming up and the oil temperature is going up so the pressure should drop a little as the oil temperature rises.
But after the TH pedal was blipped gently, suddenly, the gauge started moving in opposite direction and at the end of the video, the pressure is at about 3kg despite the oil temperature climbed throughout the video and when the rpm was almost exactly the same at the start of the video.


Therefore, personally, I'll use the gauge as reference only and not pay too much attention to the absolute number because it's not reading the actual oil pressure at the source and the reading could be different depending on many factors.











The smell of the oil from the side air vent at the right side is very likely to be the oil seeped through the valve head cover or cam oil seal landing behind the crank pulley.

You can't clean it or see it without removing several parts.

Something should look like shiny aluminum silver is probably covered in full of sticky gunk soaked in seeped oil.





For your information, as long as the followings are all true, you are very likely to be fine with the oil pressure unless you have other mechanical failures.
Even with the good oil pressure, if you don't drive regularly and allowed condensation inside the engine, that will cause other issues.



The engine is cold.

You can see the oil well above the MIN line at the oil level dip stick.

Turn the IG key into P2 ON position (lots of lights on the dash gauge) but do not start the engine.
The red OIL warning light is On.

Start the engine and almost immediately, the red OIL light would switch Off.

You can see some readings on the oil pressure gauge.

While driving or once warmed up, blip the TH pedal gently to raise the rpm.
The oil pressure gauge needle would move up a little as you blip.




As you have 2002 spec, you already have the later spec gauge.
It will fail eventually but you will notice other issues first such as BRAKE LAMP warning light stays On despite all light bulbs are fine.


If you don't see any movements when you blip the TH, you may want replacing the sender unit but the same issue may come back again unless you clean the oil passage or drive regularly.


Kaz

[Kippers]

this.

Common failure after 15 years, just the sensor reading, nothing to do with the oil pressure in the engine, the sensor is just reading low. Ignore it or replace it. I was not patient and replaced it with a new one ($280 or so).

Thank you for the re-assurance … at nearly £500 think I’ll ignore it for now.

the oil gauge sensor is at the top of the engine after everything has had oil fed to it.

the oil pressure warning light uses a sensor much closer to the oil pump and is completely separate.

the oil pressure sensor is much like a old fashioned petrol gauge mechanism, and does get 'tired'. sos offer a replacement using another manufacturers 'tweaked' sensor and remote mount, tho whether it improves the gauge reading is subject to various threads on NSXprime

Ah, never think to look on NSXPrime. Useful explanation of what’s where, thank you.

Hi, Kippers.

…. what happens while the car is parked especially if you don't drive regularly.

Very comprehensive explanation, thank you. My car gets driven just once or twice a week now but that is year round. Don’t know if that counts as “regularly” or not!

You won't be able to keep monitoring the gauge while you are driving but if you take video, from time to time, you will notice random and inconsistent pressure reading on the gauge on some of the NSX even when you think you have no problem.


Please take a look at this video. …

… Therefore, personally, I'll use the gauge as reference only and not pay too much attention to the absolute number because it's not reading the actual oil pressure at the source and the reading could be different depending on many factors.


I see what you mean, thanks.

The smell of the oil from the side air vent at the right side is very likely to be the oil seeped through the valve head cover or cam oil seal landing behind the crank pulley.

You can't clean it or see it without removing several parts.

Something should look like shiny aluminum silver is probably covered in full of sticky gunk soaked in seeped oil.

Will pass this on to the garage – the smell has definitely lessened so it may just be my paranoia now!

For your information, as long as the followings are all true, you are very likely to be fine with the oil pressure unless you have other mechanical failures.

The engine is cold.

You can see the oil well above the MIN line at the oil level dip stick.

Turn the IG key into P2 ON position (lots of lights on the dash gauge) but do not start the engine.
The red OIL warning light is On.

Start the engine and almost immediately, the red OIL light would switch Off.

You can see some readings on the oil pressure gauge.

While driving or once warmed up, blip the TH pedal gently to raise the rpm.
The oil pressure gauge needle would move up a little as you blip.

Followed this to the letter (I normally check all the lights anyway), all behaved as required.

As you have 2002 spec, you already have the later spec gauge.
It will fail eventually but you will notice other issues first such as BRAKE LAMP warning light stays On despite all light bulbs are fine.

If you don't see any movements when you blip the TH, you may want replacing the sender unit but the same issue may come back again unless you clean the oil passage or drive regularly.


Thanks for the tips. It never ceases to amaze me how much time and effort you go to to pass on your professional knowledge of the NSX - you're a star!

Kaz

Many thanks all for your very quick responses, I really appreciate you taking the time to help and put my mind at rest – the temperamental sensor will stay for the time being.
Being able to draw on the vast experience and depth of knowledge of the car on this forum is invaluable.
Thanks again,
Karen