So I’m cleaning my MAF and replacing my a/c drier...and I figure, oh while the system is empty why don’t I just change that leaky oil pressure switch (which I assume that’s what it was near the oil filter)

I get the OEM one out just fine. But then I go to install a similar looking one from import direct, and it absolutely does not fit! I’ve stood for two hours trying to get it to go in. Grease, Teflon tape, sealant. Nothing. I then try to put the original back in, and it doesn’t fit either!

I’m like what the hell!? I always get stuck on these little things that just don’t make any sense. It came out fine, but it won’t go back in. I decided to just give up and try to get a different one from a different store in the morning. No stores in the small town I’m in carry any others.

There also seems to be 2 types: one is a flat up to the thread, the other protrudes out a bit. I started looking around in case anything fell off, I didn’t see anything. So I don’t know why it’s not screwing in. Hoping it’s just a crap aftermarket part.

Also websites like Infintipartsdeal and affordableinfintiparts which I rely on for images and brought a few parts from, are incorrectly showing the position for the oil pressure switch. It’s showing it being on the oil pan side, and seems to point to a coolant temp switch on the oil filter side. The manual only points to 1 oil pressure switch by the oil filter.

Here is the correct part # for the VH41DE:
SWITCH- NISS #25240-89960

be very careful with the threads. The Nissan switches (and the casting that is threaded) use an unusual thread pitch. close isn't good enough, even with thread sealer.....

Thanks for the lead. That’s the one I got.

I went to pick up a different one but still having the same issue. Tried a torch lighter too. May have to get a tow and see if someone is good with a thread chaser. I don’t know what the hell happened. Only thing I can think of is the engine being cold the hole shrunk.

3rd nightmare of the week over something relatively simple. I’m retiring from mechanic work after this year. Newish cars only.

I picked up a tap and die set, but they handed me SAE instead of metric so I didn’t even open the box and didn’t realize til I got home. Some of these parts stores are just no help without the know how. Multiple trips for the same issue and nothing gets done.

It seems like I might be able to just sharpen up the threads and get it in. It does seem to lock and hold a little bit, but it won’t turn before falling back out. Only thing I can think of is there was so much grit and oil in there and something got fused. Like I said, even the old one won’t go back on.

Don't expect that anybody knows anything. Hell, I don't know half of what I don't know....
Do your own research. The threads *might* not be SAE OR metric. They might be British pipe, I don't remember exactly, just that they are unique. Gather all the info you can, you don't want to get this wrong.

The Nissan engine blocks use the BTS British standard thread, not SAE. You may have cross threaded the block when you tried to use the SAE replacement. Go to any auto parts store and look in the after market dials and gauges section. You will find a short BTS to SAE adapter for around $4, depending on the store pricing policy.

Thanks for replies:

I went to a hardware store and an auto parts store. The hardware store was able to size the oil pressure switch thread to a M10x1.0. They didn’t have a chaser and I went to o’reiley and they also didn’t have a chaser available for that size in their set. So I had to return that also.

Like I said, when I took the old one out, I loosened it without too much resistance, and then unscrewed by hand. I went to the auto parts place and when I came back with the new one, it would not go back on. Even the old one. It’s not even catching a thread to crossthead.

I’m going to try one more ditch effort to clean the inside of the hole with a steel brush in case there’s a piece of sand caught in there, because it was really cruddy when pulled it up.

Otherwise it’s going to be an embarrassing tow to my local mechanic shop, which has done work for me before so it’s not too bad...but very slight part of me wonders if they removed that switch earlier this year when replacing the compressor since it sits right on top of it.

And I changed it because my old compressor was covered in oil and it seems the oil pressure switch or even the gasket around the oil filter bracket is letting oil leak into the new one.

Update: so I ended up having to get towed to a shop after all. Figured it wasn’t the worst thing considering the starter was dead anyway.

But wow, what a f*** fiasco!! They called me the next morning saying they been trying for an hour to put the one in I brought from goddamn advance auto. So they ended up going back to OReiley and buying another one. And the 1st one I tried was from there. They finally got it in, saying the starting threads on the one I had were faulty. I had asked the knucklehead at advanced auto to show me another part because I didn’t feel the one he gave me matched the picture on the website (even though it did look like the one on the Nissan Diagram).

But just to make sure I wasn’t going crazy: I unscrewed the one out of my 97 Maxima which uses the same oil pressure switch, added some sealant (last time I installed it couple years ago, I didn’t know I needed to add thread sealant). It almost seemed like it wasn’t going to catch, but I was able to clean it off and get it right back in.

All in all, this has just been a nightmare week for me and the Q. All this comes right after I fixed my heater core. Going forward, I’m going to start being very gentle with this car. I have a 1,200 mile trip coming up, and I almost just don’t want to do it because I don’t want anything else breaking. But I’m hoping similar to other used cars I’ve had in the past, I go thru these things but then the car ends up being trouble free for another couple of years.

But part of me is starting to feel the pressure on both cars, that 2020 is too long to still be riding around in cars from the late 90s. But for the most part, the things that go wrong are the things that would go wrong on any car: moving parts, electrical parts, etc. it’s not like I’m having engine or transmission problems like some BRAND NEW American cars do lol.

I personally think might of happened was: when I removed the oil switch the engine was cold. The insert could have very slightly compressed. Other possibility is if someone removed and inserted it before, they might have not cleaned it enough and allowed some sand/grit grind on the entry thread. Either way, it’s another reminder why I don’t like working on a cold engine. Too much s*** goes wrong that way. I always prefer a warm engine to work on.