Jump to content
SAU Community

Oil Pressure Sending Unit

HanBear

By HanBear,
in General Maintenance

 Share

Recommended Posts

HanBear Contributor

HanBear

Posted
Posted

I've done a very thorough search and couldn't find anyone that says the exact size for the Oil Pressure Sending Unit.

I was wondering what type of thread i needed and if i can just use an autometer sending unit. Ultimately using a Autometer Oil pressure gauge?

Thank you guys!

Link to comment
https://www.sau.com.au/forums/topic/457972-oil-pressure-sending-unit/
Share on other sites
HanBear Contributor

HanBear

Posted
  • Author
Posted

Cool! Thank you guys. I'll give it a shot. Also I've read somewhere else that the 300zx sending unit is pretty much the same as the all the RB motors. so I'll give that a shot as well because i'm in the states and the 300zx parts are stupid easy to find! Another question on the Oil pressure though:

I live in AZ where the summer weather is 110degrees F.

I drove my car in California where the Oil pressure was FINE. but as soon as I came back to AZ (where I actually live) the oil pressure started to drop. Drop meaning almost to 0. then only getting up to maybe 20-30psi driving. Does Crazy hot weather have an effect on that?

Because in California like i said the oil pressure was fine because the weather is significantly cooler there.

I'm running 20w50 (switched today)

from 10w30

I thought since it's too hot here the viscosity is thinning out too much with 10w30 but even with 20w50 it's still dropping...

Is that a ambient heat issue? I'm going to try and replace the sending unit and if that fails too then I'm almost sure that I'm going to need a new oil pump which is going to cost me quite the bit of money because of Labor. (I don't have the time to be doing my own engine work ATM)

Thanks for your input guys!

Kinks Grand Master

Kinks

Posted
Posted

It is 1/8 bsp. Which is close to 1/8 npt so can work.

Yikes. Not on my car thanks. Thread pitch and included angle are both different!

http://pipeandhose.com/?q=node%2F2

The "force to screw it in" that 89CAL mentions is because the threads are binding. It's close enough to "work" - whatever that means.. but you will have a large amount of force on the 2 threads that are binding and the other threads are sitting there doing nothing. It won't be kind to either thread either.

Spot the engineer huh :P

Hanbear the 300ZX should have a water/oil heat exchanger.. primarily this heats the oil quickly to operating temp ~85C but it also means the oil shouldn't get too much hotter than that unless you're on a racetrack. 20W50 is extremely thick oil, are you using mineral or full synthetic? I only use full synthetic 5W40.

You need to state oil pressure as a function of RPM as well. For example my car gets about 2 bar (30psi) at idle and then 3-4 bar at 3000RPM once fully warmed up (driving for at least 30 minutes). My last car showed less. The standard gauges CAN be unreliable so if you suspect issues it's best to use a good quality aftermarket gauge.

Ben C34 Grand Master

Ben C34

Posted
Posted

Just to clarify there's no way I would do it or reccomend it.

I added that quickly as I have posted in previous threads on this topic and someone always comes along and says they use npt no worries.

So. To clarify. A 1/8npt male thread will fit into the 1/8 bsp female thread, poorly.

89CAL Grand Master

89CAL

Posted
Posted

Yikes. Not on my car thanks. Thread pitch and included angle are both different!

http://pipeandhose.com/?q=node%2F2

The "force to screw it in" that 89CAL mentions is because the threads are binding. It's close enough to "work" - whatever that means.. but you will have a large amount of force on the 2 threads that are binding and the other threads are sitting there doing nothing. It won't be kind to either thread either.

Spot the engineer huh :P

Hanbear the 300ZX should have a water/oil heat exchanger.. primarily this heats the oil quickly to operating temp ~85C but it also means the oil shouldn't get too much hotter than that unless you're on a racetrack. 20W50 is extremely thick oil, are you using mineral or full synthetic? I only use full synthetic 5W40.

You need to state oil pressure as a function of RPM as well. For example my car gets about 2 bar (30psi) at idle and then 3-4 bar at 3000RPM once fully warmed up (driving for at least 30 minutes). My last car showed less. The standard gauges CAN be unreliable so if you suspect issues it's best to use a good quality aftermarket gauge.

I said i needed to force it in to get it in not that i actually forced it in

I worked out it wasnt 1/8NPT then made a plan to get around this. So now i have the right fitting in the block to a braided line to an oil manifold for my sensors

HanBear Contributor

HanBear

Posted
  • Author
Posted

Yikes. Not on my car thanks. Thread pitch and included angle are both different!

http://pipeandhose.com/?q=node%2F2

The "force to screw it in" that 89CAL mentions is because the threads are binding. It's close enough to "work" - whatever that means.. but you will have a large amount of force on the 2 threads that are binding and the other threads are sitting there doing nothing. It won't be kind to either thread either.

Spot the engineer huh :P

Hanbear the 300ZX should have a water/oil heat exchanger.. primarily this heats the oil quickly to operating temp ~85C but it also means the oil shouldn't get too much hotter than that unless you're on a racetrack. 20W50 is extremely thick oil, are you using mineral or full synthetic? I only use full synthetic 5W40.

You need to state oil pressure as a function of RPM as well. For example my car gets about 2 bar (30psi) at idle and then 3-4 bar at 3000RPM once fully warmed up (driving for at least 30 minutes). My last car showed less. The standard gauges CAN be unreliable so if you suspect issues it's best to use a good quality aftermarket gauge

I'm only using the z32 Oil Sending Unit because it fits the RB series engines.

As far as the Oil pressure goes. In cool weather it operates fine. I think the standard pressure guage is in Bar increments of 2 right? 0 - 4 - 8?

If it is then here's what it's doing:

Cool weather cold start jumps to 4 then warm goes back down to about 2. and driving goes to 4.

The weather here in AZ it would operate fine when i first start the car for the day. Then I'll drive around and the pressure would go down to below the 2 at idle and then would jump to between 2 and 4 so around 3 driving. Sometimes it'll be at 2.

So I thought that since I'm driving in 110-120 degree F weather the oil is just cooking and thinning out. It's still doing this with the 20w50 in there. :(

I'm HOPING that the sending unit and Oil Cooler will get the job done with a new oil pressure gauge. If not then I know it's my pump or gap between the bearings... which will ask for a Engine Pull.... :(

I'm just hoping.... wish me luck Lol

Kinks Grand Master

Kinks

Posted
Posted

yeah the standard gauge is kg/cm^2 which is almost identical to bar (there is a 2% difference which can be safely ignored).

the standard gauges are known to be quite inaccurate. from "not bad" to "substantially wrong" depending on your luck :)

my R33 used to idle at 2 bar but when the oil was close to changing would sometimes drop to 1 bar (or less) at idle and only 2 bar while driving (~3000RPM). certain brands of oil showed this characteristic more, some less. I suspect the gauge was overly sensitive around the lower end of the scale TBH

never had a problem with the motor though, I drove it like that for over 100,000km :) so I don't think you need to panic about engine pulls just yet. Get an aftermarket gauge on it just for peace of mind though.

ALL oils lose pressure when they warm up - they get less viscous which means less resistance to flow. Synthetic oils are naturally better at maintaining viscocity when hot, that (and their superior lubricating ability) is why we all recommend them.

HanBear Contributor

HanBear

Posted
  • Author
Posted

Well thank you all for your inputs! I replaced the sending unit with a z32 sending unit today. The oil pressure is holding steady and fine. Luckily for me. Haha. So far.... I haven't driven too much on it but I'll see how it goes. So far it seems that the only thing wrong was my sending unit. Haha. Thanks again y'all!!!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • RP1421
      S15 Spec R

      By RP1421 · Posted

      As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • joshuaho96
      R32 GTS (RB20DE) Injectors Replacement

      By joshuaho96 · Posted

      I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
    • perry_r33
      R34 GTR Vspec Garage Sale - All must go!

      By perry_r33 · Posted

      Pm sent 
    • Robot
      Skyline v36 350GT sedan hunting on idle

      By Robot · Posted

      Hi,  Just joined the forum so I could share my "fix" of this problem. Might be of use to someone. Had the same hunting at idle issue on my V36 with VQ35HR engine after swapping the engine because the original one got overheated.  While changing the engine I made the mistake of cleaning the throttle bodies and tried all the tricks i could find to do a throttle relearn with no luck. Gave in and took it to a shop and they couldn't sort it. Then took it to my local Nissan dealership and they couldn't get it to idle properly. They said I'd need to replace the throttle bodies and the ecu probably costing more than the car is worth. So I had the idea of replacing the carbon I cleaned out with a thin layer of super glue and it's back to normal idle now. Bit rough but saved the car from the wreckers 🤣
    • GabsReDeal
      R32 GTS (RB20DE) Injectors Replacement

      By GabsReDeal · Posted

      After my last update, I went ahead with cleaning and restoring the entire fuel system. This included removing the tank and cleaning it with the Beyond Balistics solution, power washing it multiple times, drying it thoroughly, rinsing with IPA, drying again with heat gun and compressed air. Also, cleaning out the lines, fuel rail, and replacing the fuel pump with an OEM-style one. During the cleaning process, I replaced several hoses - including the breather hose on the fuel tank, which turned out to be the cause of the earlier fuel leak. This is what the old fuel filter looked like: Fuel tank before cleaning: Dirty Fuel Tank.mp4   Fuel tank after cleaning (some staining remains): Clean Fuel Tank.mp4 Both the OEM 270cc and new DeatschWerks 550cc injectors were cleaned professionally by a shop. Before reassembling everything, I tested the fuel flow by running the pump output into a container at the fuel filter location - flow looked good. I then fitted the new fuel filter and reassembled the rest of the system. Fuel Flow Test.mp4 Test 1 - 550cc injectors Ran the new fuel pump with its supplied diagonal strainer (different from OEM’s flat strainer) and my 550cc injectors using the same resized-injector map I had successfully used before. At first, it idled roughly and stalled when I applied throttle. Checked the spark plugs and found that they were fouled with carbon (likely from the earlier overly rich running when the injectors were clogged). After cleaning the plugs, the car started fine. However, it would only idle for 30–60 seconds before stalling, and while driving it would feel like a “fuel cut” after a few seconds - though it wouldn’t fully stall. Test 2 – Strainer swap Suspecting the diagonal strainer might not be reaching the tank bottom, I swapped it for the original flat strainer and filled the tank with ~45L of fuel. The issue persisted exactly the same. Test 3 – OEM injectors To eliminate tuning variables, I reinstalled the OEM 270cc injectors and reverted to the original map. Cleaned the spark plugs again just in-case. The stalling and “fuel cut” still remained.   At this stage, I suspect an intermittent power or connection fault at the fuel pump hanger, caused during the cleaning process. This has led me to look into getting Frenchy’s fuel hanger and replacing the unit entirely. TL;DR: Cleaned and restored the fuel system (tank, lines, rail, pump). Tested 550cc injectors with the same resized-injector map as before, but the car stalls at idle and experiences what feels like “fuel cut” after a few seconds of driving. Swapped back to OEM injectors with original map to rule out tuning, but the issue persists. Now suspecting an intermittent power or connection fault at the fuel pump hanger, possibly cause by the cleaning process.  
×
×
  • Create New...