Oil Pressure Sensor: which sealant/adhesive to use on threads??

mudgudgeon

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I use a small amount of teflon tape.

Spent time as a plumber, taught by old school tradies.

If teflon tape is applied to the threads properly, there's no way it can migrate INTO the hole.
The action of screwing the fitting in will push / compress the tape up the fitting thread, NOT into the hole.
Same with pastes and thread lockers, as you screw a fitting in, a lot of the paste stays put, and the thread has less and less paste on it the further you screw it in

Lots of people, plumbers included don't do a good job with teflon because they don't understand it.

I never liked thread sealing pastes. Lazy people really on them too much IMO (that's not to say they don't have a place). I've seen leaks that don't make sense where paste sealed joints have failed. Seen it as a plumber (workmates used it), and as a builder.
I've talked to owners of plumbing companies who don't allow their guys to use it, and get pissed off when they do.
 

mudgudgeon

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My buddy is a union plumber in Boston and they have to paste and tape all threaded joints.

Have used this method as a plumber as well. IMO if tape is used correctly, paste isn't contributing anything to the joint, it's compensating.

If a paste sealed joint has to be undone and redone, paste is a disadvantage as it hardens, and don't separate cleanly. Then when redoing the joint, you are trying to seal an uneven surface if all dry past isn't removed.

This is why I use tape on engine sensors. It's easier to remove a little tape residue out of threads in a head it block than it is to remove dry paste/glue when that sensor has to be replaced in the future
 

micruz60

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My buddy is a union plumber in Boston and they have to paste and tape all threaded joints.
Seems like a diaper-plus-suspenders approach.

I miss the traditional approach of sweating the joints with solder. Too expensive to do copper anymore, of course drain pipes are seldom cast-iron too.
 
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AFAIK the BSPT type threads of the oil sensor seal fairly well by themselves so a thread locker (which also seals) may be why Toyota specified what they did for that application?? IDK

In contrast I just removed the "gas" (vacuum) filter on the top front of intake
of a 97 FZJ80, it had what looks like grey FIPG around it's threads. Those threads appear to slightly tapered?? Double checked on a 96 FZJ80, same thing. So for that application maybe a perfect air tight seal is more important?? I couldn't find that spec in the FSM, probably missed it as my copy is falling apart and in a few pieces.

FWIW

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Njck22

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AFAIK the BSPT type threads of the oil sensor seal fairly well by themselves so a thread locker (which also seals) may be why Toyota specified what they did for that application?? IDK

In contrast I just removed the "gas" (vacuum) filter on the top front of intake
of a 97 FZJ80, it had what looks like grey FIPG around it's threads. Those threads appear to be metric, not BSPT. Double checked on a 96 FZJ80, same thing. So for that application maybe a perfect air tight seal is more important?? I couldn't find that spec in the FSM, probably missed it as my copy is falling apart and in a few pieces.

FWIW
It's probably the case that the vacuum being pulled on the gas filter is low enough to where tapered thread sealing is unnecessary and dope on the straight threads is good enough. For the oil pressure sensor, using dope is the "correct" way on any hydraulic system because there is no risk of it blocking a port in the system, and from a manufacturing POV, its much easier to apply dope to threads and assemble than have some Japanese guy spending all day putting exactly 2.5 wraps of telfon tape on every oil pressure sensor.

That being said, using oil resistant teflon tape is a 100% valid way to do it, as I do, just be careful not to block anything
 
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OK, good info. I went back and compared the gas (vacuum) filter threads with a few small metric bolts and with a micrometer, the threads appear to be slightly tapered and maybe BSPT?? I applied a small amount of Honda Bond FIPG to those threads (what was there originally looked/felt like old grey FIPG) when I installed it.

Also FWIW the gas filter did screw in like a tapered thread, getting progressively harder to turn and all the threads do not go in the hole, there's a ~3.3mm gap between the back of the filter housing and the front of the milled space on the intake. Compared to an original untouched factory installed filter and that gap was the same.
 
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