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Apr 11, 2020

Nissan Skyline Oil Pressure : Oil Pressure Senders : Bad Oil Pressure Readings

Kaizo R34 GT-R on set of Fast and Furious 4
R32, R33, R34 GT-R ( Also AWC34, S15, W11, S14, Z32) all use the same oil pressure sensor

Two fold issue with oil pressure, and oil pressure sensor or sender on Nissan Skylines, they use the same sensor as a 90-96 300ZX, and they are known to read low.  Internally the parts of the sensor can fail, and they also have a small inlet that can clog.  
25070-30P01 Nissan Skyline GT-R oil pressure sensor also 300zx
25070-30P01 Nissan Skyline GT-R oil pressure sensor also 300zx

This would be considered normal idle oil pressure at operating temperature for a Nissan Skyline GT-R


Jun oil pump, broken at the flats. This will cause low oil pressure

Low oil pressure, can be a real thing with an RB. Cracked oil flats, backed out oil pump screws.   So how do you know if its actually lost oil pressure, or if the sender is bad? If you did normally lose actual pressure, assuming its not something like the screws backing out of the oil pump, probably soon, the engine starts making really expensive sounds, and eventually, just stops running. This is a bad thing. So you really need to treat every low oil pressure situation that is new, as a real oil pressure problem. 

Engine Lubrication and Cooling Fluid Capacities for Nissan Skyline

Engine Oil Capacity (quarts)
H Level4.24.34.8
L Level3.23.53.7
Oil and Filter Change~ 4.4~4.8~4.9

Coolant Capactiy (liters)

Engine Oil Pressure(kg/cm2, psi)
RB20E~1.0, 14~3.8,54~4.8,68
RB25DE~1.0, 14~3.3,47~5.3,75
RB25DET~1.0, 14~3.5,50~5.6,85
RB26DETT~1.5, 21~3.0,43~4.6,65

From the factory service manual, you remove the sensor, put a mechanical gauge on it, and check for oil pressure at operating temperature. If it fails these tests, you will need to investigate further.  "The Oil Pressure Sending Unit uses a ⅛ BSPT, as do most aftermarket OPSUs (at least, those from Japanese manufacturers). NISMO once sold a T-Fitting to run two oil pressure sending units (ie, stock and aftermarket), which was basically a three-way female ended ⅛ BSPT T-Fitting with a male-male ⅛ BSPT adapter on the end. P/N 25073-RN010, this part is no longer available."

Even though it says oil pressure switch, it is the sensor. It drives the gauge in the dash

Oil pressure sender

Inside an OEM Oil pressure sensor : Not my picture, saved this a while back
Inside an OEM Oil pressure sensor : Not my picture, saved this a while back

R32, R33, R34 GT-R ( Also AWC34, S15, W11, S14, Z32)

Nissan OEM oil pressure sender  - 25070-30P01    alternate  25070-30P00
Beck Arnley - 201-1469

I do think that if you remote mounted the oil pressure sensor, it may have a longer life.  It is hard mounted to the oil filter block, and sees a lot of heat and vibration. By finding the right fittings, and some steel braided line, you could probably greatly increase its life, by remote mounting it. 

This oil pressure sensor instructions, say DO NOT INSTALL SENSOR ON ENGINE DIRECTLY

Why do the oil pumps fail or you get low oil pressure?

  • Installation error. If the pump is not square to the block and crankshaft, it will bind with every turn of the engine. We have seen several failures related to new builds, align honed, and the pump dowels not being modified to ensure the gear clearance is correct. 
  • Cavitation at the inlet side of the pump.  High RPM, long draw. Pumps only like to do one thing, suck or push. You are asking it to do two, which it doesn't want to do. 
  • Bad design. The flats of the drive are at the small side of the gears. If the pump cracks, it normally pushes oil out of the front main seal.  If you change it three times and its still leaking oil, you probably broke the oil pump.  Ask me how I know. 
  • Going oval. We have seen the gears go oval. Mostly related to install, and cavitation. 
  • Backing plate screws coming loose.  The backing plate screws can come loose causing a loss of oil pressure. Loctite or stake them in place when assembling engine. 
Oil pump screws backing out, causing an internal oil leak. Change your damn oil more often. From Skylife

This video from Real Street Performance shows Jay go over how to take apart and inspect a 2JZ oil pump prior to installing it on an engine.  While an RB isn't a 2JZ, they both are similar style of pumps, and what goes for 2JZ generally goes for RB. 

In today's video Jay goes over how to install a new OEM 2JZ oil pump. This is a quick guide to help you properly install a oil pump to avoid any issues in the long run. If you have or have not installed a 2JZ oil pump before, This video can be really helpful as there are key points to avoid common failures. If you have any questions or need help with your project, feel free to reach out to us.

- OEM 2JZ Oil Pump Assembly:
-  OEM 2JZ Crank Seal:
- Small O-Rings (Contact us to order) 96721-24022 & 90301-A0032

00:00 Introduction
00:19 Taking the pump apart
01:00 A look inside
01:55 Lubricating the Pump  
05:12 Installing Front Main Seal
07:51 Reassembling the pump
09:33 Installing pump into engine

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