Need Help Removing Oil Pressure Switch

[Christ]

No input on thread size, but I don't recommend using brass fittings...

1. Galvanic corrosion between dissimilar metals.

2. Brass will work harden with heating/cooling cycles, and can start leaking/break off.

Aluminum fittings, if you can find them, thermal plastic, or steel/iron.

[Safety Guy]

John, before going out to my garage, I looked on Rockauto's site to see if any dimensions on the oil pressure sensor switch were there. Yep:

http://www.rockauto.com/catalog/moreinfo.php?pk=944535

In case it doesn't show up, it says:

1/8-28 ISO Tapered Thread

It says the switch closes at from 3 to 9 psi. That is for the Airtex/Wells part. It was the only brand that had any thread size info.

I also looked up a 1996 Aspire. Same part. Everything looked the same for the 1994 Mazda 323 as well. Standard B3/B6 switch, evidently.

I think this should do, unless someone knows different! Then I could go out and get greasy for ya to make absolutely sure.

Karl

[DriverOne]

Escort console is screwed into existing lower mounting points for the stock Festy console. Now I need to figure out what to do with that gap....

CB Radio :-D

[JohnGunn]

No input on thread size, but I don't recommend using brass fittings...

1. Galvanic corrosion between dissimilar metals.

2. Brass will work harden with heating/cooling cycles, and can start leaking/break off.

Aluminum fittings, if you can find them, thermal plastic, or steel/iron.

Sounds like you know what you're talking about, and I don't know enough about this to doubt you. But let me ask you to put on a different hat. Let me ask you, not what you think are the worst things that could possibly happen, but based on your knowledge and experience, what is most likely to happen.

In my gauge kit all the fittings are brass, including several adapters as well as both ends of the hose attached to the gauge. But my kit is clearly intended for occasional use by mechanics to diagnose engine problems. In that short time I'm assuming nothing bad could happen.

Accepting what you say about brass fittings, and I do, the next question would be to ask at what rate the deterioration progresses. I'm looking at one of the brass tubes that came with my set. It seems pretty substantial; I can't feel any give when I squeeze it between my fingers. My caliper says its walls are about 1.5 mm thick. How many miles of normal driving would you estimate it would take to make this tube leak? How many miles till the brass became so brittle it would break? Would the process be affected by the use of Teflon sealing tape as is recommended in my Aspire Ford Service Manual? Would that not effectively slow the corrosion process by reducing the degree of dissimilar metal contact?

In this area where the theoretical meets the real world, things become less clear. And added to that, we are dealing, not with engine designers or professional race mechanics, but with a bunch of guys trying to keep their dying breed of automobile running for a few more years.

Since you're a member here, maybe you're also one of those. So let me ask you a direct, practical question. What would you do if you wanted to extend out from a threaded connection in an iron block on your aging Festiva? Would you use the cheap and readily available brass fittings or go to the bother and expense of finding something better suited to the application?

I'm hoping there is an acceptable solution and that you will tell me steel/iron fittings are available and don't cost any more, but that is just my imagination putting words into your mouth. Could you comment on where we might find the acceptable options you mentioned.

[JohnGunn]

John, before going out to my garage, I looked on Rockauto's site to see if any dimensions on the oil pressure sensor switch were there. Yep:

http://www.rockauto.com/catalog/moreinfo.php?pk=944535

In case it doesn't show up, it says:

1/8-28 ISO Tapered Thread

It says the switch closes at from 3 to 9 psi. That is for the Airtex/Wells part. It was the only brand that had any thread size info.

I also looked up a 1996 Aspire. Same part. Everything looked the same for the 1994 Mazda 323 as well. Standard B3/B6 switch, evidently.

I think this should do, unless someone knows different! Then I could go out and get greasy for ya to make absolutely sure.

Karl

Good find, Karl. And so much cleaner.

In that long list of OEM part numbers, the one assigned by Ford to the oil pressure switch for our cars is F0BZ9278A.

After looking around the Internet a while I found that the ISO standard 7.1 is the same as the standard for British Standard Pipe Taper (BSPT) and something called Japanese Pipe Taper. The last two are defined graphically on this page. It was on this page that I first discovered the connection between the British/American tapered thread standard and our Japanese engines.

I found on this page some interesting ideas about screwing a 1/8-27 NPT threaded fitting into a hole with 1/8-28 BSPT threads. Essentially they were suggesting that they are close enough to go together and seal, with tape, of course.

I would bet the fact that there is no 1/8-28 to 1/8-27 adapter in the Harbor Freight oil pressure test kit I bought is because they look to be so close that people assume them to be the same and just screw them together and move on without knowing they have violated some fundamental law of the mechanical universe.

I would even say, if I tried to install a 1/8-NPT 27 into a Festiva/Aspire oil pressure port and it turned in 3 or 4 turns before getting tight I would think all was well. Even now that I know it is not really correct, if it went together smoothly and felt good and strong and tight, I think I might just cover the threads with a goodly amount of Teflon tape and check it carefully to make sure it didn't leak. It's probably done thousands of times a day over the whole of the world.

But, before going that route I should probably try and find an adapter. This whole matter makes me feel somehow extremely uncomfortable. Like really wanting to do the perfect thing, only to find that it entails swimming two miles upstream against a stiff current for no apparent gain.

[Safety Guy]

Ha! At from "3 to 9 psi" I don't think it would be that critical. But I could be wrong!

I can't wait to get my own set of gauges and install some good info meters.

So much to do (cars, house, yard, my weight, etc.) and I SO LAZY!! :p

Karl