I had what I thought was a simple question with a simple answer and all a Google Search has yielded is conflicting answers.

Questions:

Is Loctite Blue 243 okay to use on 1/4" NPT diesel fuel fittings ?

Is Loctite Red 272 okay to use on 1/4" NPT diesel fuel fittings ?

Some guy says he sealed a bunch of diesel fuel fittings with Loctite 572 and hasn't had a minutes trouble in over thirty years; I can't for the life of me find any other reference to a Loctite 572 and have to wonder if it is a misprint and he meant to say 272..

Reason I am asking, I have used Teflon Tape for years and years and have never had a drip nor any negative issues at all; but then, unlike most, I do know how to wind Teflon Tape on a fitting.

That being said, twice in the last few generations, once many years ago and again just the other day, I have had somewhat long fitting assemblies to "wrench" themselves loose; both instances on my manual fuel selector valves.

To be clear, this hasn't happened going down the road; but, after I have had the assemblies out for whatever reason and have reinstalled them and then given them the once-over before turning loose the fuel and heading down the road

The most recent episode caused me to have to completely dis-connect all fuel lines, remove the assembly, and start over; as, the one that wrenched itself loose had a 45° elbow and the other fittings had to be taken out of the way to tighten it back up again.

As, once I get an assembly put together, there will never be any reason to ever take it apart again; I got to thinking that, if I had some sort of permanent thread locker that would also act as a sealer, then inadvertently loosening a fitting would no longer be possible and never more be a problem.

Once I get all four legs down and away from the selector valve, which is right against the floor-board, and pointed in the four separate directions, the actual fuel lines connect via JIC Swivels = no kinking hoses, no hose clamps, and no hose barbs.

There are two identical 4-position 4-line valves residing beside one another; hence, even more reason for some longish assemblies that do have a bit of leverage against the initial connection at the valve itself.


Another thought I have had is, seeing as how the direction these fittings point, with just a degree or two one way or the other causing interference with something else, and NPT not being the friendliest medium to work with when one needs a fitting turned another 90° and it is already tight enough to split a housing; if I am using a thread locker, theoretically, I could apply the thread locker and hand-tighten the fittings, and the thread locker both weld the fitting in place and seal the threads against leakage, right ?

I keep getting pointed toward thread sealers, pipe dope, and such and that is NOT what I want as any of those things can easily be wrenched loose; ---- plus, I have not used a thread sealant yet that didn't harden inside the fitting and turn a whole bunch of hardened crumbs loose inside the system whenever the fitting is removed, hence my preference for Teflon Tape.

 

Permatex #2 is best on fuel and gas. Put some beetle juice on that thing.

 

Thanks for the input.

I use Form-a-Gasket #2 by the gallons and am well familiar with it; I was using it way back when it was Mr. Gasket; it does not LOCK the threads; I need the threads locked from loosening once I get them where I want them.

 

How about solder?

 

Now there is an option I hadn't thought of; maybe even Silver Solder as well as all components are Brass.

Of course, I would need to remember to gut the valve first, a very simple procedure, as there is a plastic Delrin cone inside that might not survive the heat involved.

One thing for certain, if anything moved again, it would be because it broke.

 

I put loctite red on my f250 mirrors years ago to prevent theft. SOB if they did not try anyway. Broke bolt was on the ground.

Better clean it good to get fuel out first! Or use a non flammable gas to fill the tank and lines.

 

Years ago a friend of mine soldered razor blades inside his hubcaps to prevent theft. It worked!

 

The stuff with the brush in the can? I got into a heated discussion about that stuff with gasoline recently.

 

Another way to guarantee that nothing ever gets loose is to use locking wire. On bolt heads, drill a 1/16" - 3/32" hole through the head and lock the bolts to each other with locking wire. On nuts and pipe fittings, drill a similar hole through the high point of the hex. When using locking wire, make sure that when tightening the wire that it is the direction of tightening the bolt, nut or fitting and not loosening it.
If it is just a nut, an alternative way is to drill right through the nut and bolt and use a cotter pin.

 

Thanks; just the other day, I used the cotter-pin through the bolt/nut on my A/C compressor pivot bolt; I have used that method a number of times.

 

Years ago when I was working I used Permatex liquid teflon. It came in a small bottle with a brush and was like a thick liquid but when it set it prevented leaks and acted like a thread locker. It would come apart but you had to put ALOT of muscle into it. I am not talking about the stuff that looks like tooth paste. It looks like a heavy pure white liquid and I only seen it made by Permatex [#80632 ] Mike

 

I used the toothpaste type working on the pipeline. Threads on bolts for access holes on tanks on the tank farm. Not exposed to the fuel.

 

I wonder if the greenies will take shellac off their **** list now that the self proclaimed elite want us to eat more bugs.

 

I like to use crosscheck. I use orange and just put a dab on the head of bolts after they're torqued. I can check at a quick glance to make sure everything is still tight.