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Oil Pressure Switch thread pitch?

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Old 07-13-2019, 03:55 PM
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Question Oil Pressure Switch thread pitch?

Hi Everyone,

SUMMARY:
Does anyone know the correct thread pitch for the oil pressure switch (part number: 25240-4M40E)?



It seems that it should be 1/8-27 NTP but I'm now not sure.

DETAILED:

My wife's '07 G35 sedan (V36) started displaying the low oil pressure indicator when idling at lights.


As you likely know, low oil pressure can be the first sign of an engine rebuild! Or, just a faulty switch or low on oil. The oil level was fine and I change it on schedule.



The car has under 46K original miles so it seemed very unlikely that it was actually low pressure. But, being the Pedantic Mechanic I wanted to first screw in an oil pressure gauge to read the actual pressure.



I bought this OTC kit that should have all of the necessary fittings and a new oil pressure switch from my local Infiniti dealer to replace anyway ($23.20 out the door).




What's odd is that the new switch will thread fine into a female 1/8-27 NTP fitting but, the male fitting wouldn't thread into the block!



In the end I gave up on trying to see the actual pressure and just replaced the switch which seems to have fixed the issue. But, it still bothers me that I was unable to use my new oil pressure gauge and to verify the actual oil pressure.



So, does anyone know the actual thread pitch?

Thanks in advance!
Larry.
 
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Old 07-13-2019, 04:10 PM
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Be aware that the oil pressure light being on like that (unless from actual low crankcase volume) is usually caused by ruptured galley gaskets.

I would just go buy another OEM sensor from your local Nissan, they're very common (EDIT: and only about $25) and were interchanged across a LOT of vehicles so they should definitely have one in stock. Should be part number 25240-4M40E which superseded the original part number 25240-4M400.

The reason it won't fit is these engines use BSP - British Standard Pipe threads, not NPT - National Pipe Thread. 1/8 BSP is actually 1/8 - 28
 
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Old 07-13-2019, 04:14 PM
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Originally Posted by [email protected] View Post
Be aware that the oil pressure light being on like that (unless from actual low crankcase volume) is usually caused by ruptured galley gaskets.

I would just go buy another OEM sensor from your local Nissan, they're very common (EDIT: and only about $25) and were interchanged across a LOT of vehicles so they should definitely have one in stock. Should be part number 25240-4M40E which superseded the original part number 25240-4M400.

The reason it won't fit is these engines use BSP - British Standard Pipe threads, not NPT - National Pipe Thread. 1/8 BSP is actually 1/8 - 28
Yea, I did buy the new switch yesterday to install anyway (it's in and seems to have fixed the issue). But, I still wanted to know that the oil pressure was correct.

Now I get to search for an adapter for this gauge .

Thanks!
Larry.
 
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