bottom oil pressure sender bolt

[leexong77]

Hi, All. I posted a thread not too long ago about my oil pressure. http://www.nsxprime.com/forum/showthread.php/170271-another-Oil-pressure-Vtec-question-Please-help .

Now, I'm trying to do a O/P test. My question is how do you get the bottom sender bolt off? The bolt itself look to be different then your normal bolt sockets. I know that there are two 10mm bolts on top that I can check the O/P from but when I tried it I got no readings at all. The O/P gauge inside the car reads about 2 to 3 bars but the O/P gauge tester reads nothing. Am I doing it wrong? So, I figure I'll try to do it from the bottom to see if I'll get any pressure. I know the car is running fine and I'm getting pressure. It's just that the O/P readings are not consistent. I hope this all makes senses.....

Thanks

 

[K1ng124]

That's strange, I thought they were identical??

 

[Old Guy]

See the attached picture showing the oil presure sending unit. The two bolts on top of the fitting bolt the fitting to the block, there is no oil pressure at these locations. What bottom third bolt are you talking about?

In order to measure oil pressure at the sending unit location, you would have to unscrew the sending unit from the fitting on the engine and get a suitable adaptor to screw your test gauge on to the fitting. I have never fiddled with mine so I don't know whether the fitting is a common NPT thread.

The service manual recommends doing the test from the oil switch port at the base of the oil filter. See the attached picture from the manual.

2 - 3 Bars is about 30 - 45 PSI which is good oil pressure if it is measured at idle.

 

[leexong77]

Sorry, what I meant was the oil pressure switch. I was following the manual guide but got stuck with trying to take off the OP switch. Mine dosen't look like a normal socket shape? Is that normal or is it just on mine car. I try using the sockets that I have but nothing seem to fit right. But yeah, I was trying to hook my test gauge as how the manual suggested. The two 10mm bolt that I mention are the two that sits on top of the head on the driver side near the two spool valves. I was told that we can get pressure there too.

 

[Old Guy]

The oil pressure switch should just screw out of the oil filter base (see the area circled in red in the attached picture). If your oil pressure gauge has a 1/8" pipe thread on it, it should just screw into the boss that the pressure switch threads into. Should be easy (other than being in an awkward location). Sounds like you may have some different arrangement.

 

[leexong77]

Wow!! Thanks for the images, this really helped. I'll just have to try to see what socket that'll fit. Mine might just have some thread lost on the OP switch. I hope that won't be too much of a pain in the a$$ because of that. Again thanks for the time and effort.

 

[Daedalus]

I'm not 100% certain, but I think the threads are BSPT threads, not NPT, which most gauges use. But the 2 are very close in pitch @ 1/8" (27 threads/inch vs. 28 threads/inch), so it will actually seem to start just fine, but only for a couple turns before binding up. Forcing it is a great way to ruin the threads, especially in aluminum. Again, not 100% certain, but keep it in mind. Seems common for Japanese cars to have BSPT threads on their oil fittings.

 

[Old Guy]

You are correct and good catch. The procedure I attached from the shop manual does specify that the oil pressure switch boss has 1/8" BSPT threads. If you are not using a Honda specific tester, then it is likely that the tester has NPT threads.

I'm not 100% certain, but I think the threads are BSPT threads, not NPT, which most gauges use. But the 2 are very close in pitch @ 1/8" (27 threads/inch vs. 28 threads/inch), so it will actually seem to start just fine, but only for a couple turns before binding up. Forcing it is a great way to ruin the threads, especially in aluminum. Again, not 100% certain, but keep it in mind. Seems common for Japanese cars to have BSPT threads on their oil fittings.