Thread sealants

[FLYWHEEL]

Hi,
A quick question, which thread sealants do you use for fuel fittings etc on your vehicles.
I am about to bypass my FDC and want to plug up the holes instead of looping the fuel lines. I don't realy want to use Teflon tape and would rather use a paste or liquid sealant.
So what are your suggestions?

 

[frank8003]

There is a reason the fuel lines are looped instead of being removed?

 

[cattlerepairman]

I thought the reason was to make it as simple as possible and use parts that already exist on the truck, rather than introduce new (such as plugs).

 

[FLYWHEEL]

I thought the reason was to make it as simple as possible and use parts that already exist on the truck, rather than introduce new (such as plugs).

I think that I will have to introduce new parts anyway as I think that my old fuel line may be brittle and break when trying to loop them.

 

[FLYWHEEL]

There is a reason the fuel lines are looped instead of being removed?
View attachment 760930

View attachment 760931

View attachment 760932

Even if I loop the fuel line I still have to swap the T fitting with the elbow, and will need to seal the threads on them.

 

[frank8003]

I thought the reason was to make it as simple as possible and use parts that already exist on the truck, rather than introduce new (such as plugs).

I never could figure an answer about reason it is looped, it is logical to just save the fittings and such but always wondered why. Perhaps there is fuel/hydraulic issues. I leave it to floridison or rustystud whom have rebuilt the FDC. They would have the definitive answer.

https://www.steelsoldiers.com/showt...ctions-to-bypass-the-Fuel-Density-Compensator

 

[Floridianson]

No pressure of any kind at the FDC when by passed so just use NPT plugs and nothing on the threads just remove the fittings. As for the T on the over flow valve it is inverted flair nothing needed there.

 

[Floridianson]

Double post but since it's here I never use Teflon tape on an injection system. I have some liquid stuff called Blue blocker. Also don't waist time trying to undo the lines from the fittings just use side dikes and clip off the lines right at the fittings and as said remove them. At the T fitting your just using the inverted flair plug on one part of the T fitting the rest stay there as you need the over flow valve in place and working.

 

[gringeltaube]

I never could figure an answer about reason it is looped, it is logical to just save the fittings and such but always wondered why. ................

Posted 10 years ago, by our senior expert: https://www.steelsoldiers.com/showt...nsator-by-pass&p=345842&viewfull=1#post345842

 

[FLYWHEEL]

Double post but since it's here I never use Teflon tape on an injection system. I have some liquid stuff called Blue blocker. Also don't waist time trying to undo the lines from the fittings just use side dikes and clip off the lines right at the fittings and as said remove them. At the T fitting your just using the inverted flair plug on one part of the T fitting the rest stay there as you need the over flow valve in place and working.

Thank you for your posts, very informative and helpfull

 

[Floridianson]

Two more inverted flair plugs and you could take out the flame heater from the system. Only if you thought it might give you problems. One on the over flow valve T and the last one on the injector return lines.

 

[frank8003]

There is five ways to put fuel into the crankcase of a multifuel that one does not want.
O-rings are your friend.

O-Ring History original 02132013
Niels Christensen perfected and patented the o-ring.

An o-ring is a solid rubber seal shaped like a doughnut or torus. When pressed between mating surfaces, an o-ring blocks the passage of liquids or gases.

Patent Drawing for the O-Ring

An o-ring is a solid rubber seal shaped like a doughnut or torus. When pressed between mating surfaces, an o-ring blocks the passage of liquids or gases.
Niels Christensen
Independent inventor, Niels Christensen perfected the o-ring while developing automobile brakes. Christensen received a patent for his improved o-ring in 1937, however, manufacturers were not interested until the aircraft boom of World War II. Then Christensen was able to sell his o-rings to the military after tests on a Northrop plane. The simple o-ring enabled a complex technology to advance.

Background O-Rings
Early uses of round, resilient rings for dynamic applications were in long grooves or as seals in between sliding telescope tubes or on pistons where the rings were not confined, allowing them to slide back and forth. These were not effective. Large cross-section india rubber rings were used as gaskets in counter-bores for water-works piping in the mid 19th Century. Thomas Edison's 1882 light bulb patent shows a round rubber ring at the neck of the glass bulb to keep the mercury in and the air out. There is a Swedish patent for an o-ring that is dated May 12,1896.

Dynamic O-Rings
Today's dynamic o-ring in a short rectangular groove was the result of experimental work in the early 1930's Niels Christensen. By the early 1940's, o-rings became the standard seal for the Air force hydraulic systems. This established the basic sizes and design information. In the 1950's, came acceptance for industrial hydraulics, farm equipment, passenger cars accessories, plumbing, appliances, pumps, valves, and many other devices. Today, billions of o-rings are sealing every conceivable apparatus all over the world, in the air, on land, and sea, and in outer space.

O-Rings the Seal of the Century
The o-ring is the most widely adapted seal in history because of its simplicity, low cost, ease of installation, and small space requirements without supporting structures. It is suitable for dynamic or static seals within the temperature limits of elastomeric materials, Successful use depends upon proper groove dimensions and selection of the right compound, or from one's prior experience with similar applications.

If one goes thru the trouble to replace o-rings then do not quibble, just use viton.
https://www.marcorubber.com/o-ring-size-chart-index.htm

And DO NOT put multifuel or any diesel crankcase oil into your your diesel engine as fuel.
Do NOT just run that so called diesel fuel solely in your multifuel, it has no lubrication.

 

[davidb56]

good reading.......https://www.fuelexpert.co.za/2-stroke-oil-in-diesel-technical-study.php

 

[davidb56]

this one is good too, especially toward the end when talking about additives and fuel "gel". https://www.petrolplaza.com/knowledge/1982

 

[davidb56]

last one........we can ignore mis fueling for the multifuel, but some injector cleaners may not provide lubrication. https://blog.motoringassist.com/car-maintenance/prolonging-diesel-injection-pump-life/

 

[rustystud]

Hi,
A quick question, which thread sealants do you use for fuel fittings etc on your vehicles.
I am about to bypass my FDC and want to plug up the holes instead of looping the fuel lines. I don't realy want to use Teflon tape and would rather use a paste or liquid sealant.
So what are your suggestions?

I use "Permatex" 80631 for sealing all my pipes and fittings. Whatever you use, make sure it is "fuel rated" ! There are plenty of pipe sealants out there, but only a few are rated to handle fuel and hydraulics.

 

[41cl8m5]

I have done some research into fittings and DOT requirements and found a substance called Vibra-Tite. it is the red stuff you will see on the pipe threads of fittings with DOT approval. Now the stuff is not cheap and I use it at my work. MSC carries it. It takes some time to dry before installing and it will not come loose on its own. Kind of like hard sticky rubber. Now loc-tite thread sealer has different kinds for different purposes two are like liquids teflon and one will harden after installed but both are just for sealing my still become loose by vibration. We use all kinds of sealants at my work and the ones I mentioned above are used for pipe threads.

I work in a manufacturing plant building machinery that most of the world these days needs. Running weight of the equipment I work on is about 60,000 to 70,000 lbs depending on the options.

 

[rustystud]

I have done some research into fittings and DOT requirements and found a substance called Vibra-Tite. it is the red stuff you will see on the pipe threads of fittings with DOT approval. Now the stuff is not cheap and I use it at my work. MSC carries it. It takes some time to dry before installing and it will not come loose on its own. Kind of like hard sticky rubber. Now loc-tite thread sealer has different kinds for different purposes two are like liquids teflon and one will harden after installed but both are just for sealing my still become loose by vibration. We use all kinds of sealants at my work and the ones I mentioned above are used for pipe threads.

I work in a manufacturing plant building machinery that most of the world these days needs. Running weight of the equipment I work on is about 60,000 to 70,000 lbs depending on the options.

I know there are plenty of good sealants out there, but for a reasonable price the "Permatex 80631" works just fine. We used it on our busses in the transit department. No need to spend an "arm and a leg" for the same result.
Just my .

 

[frank8003]

Don't use whatever it is they put on the threads of the outlet of the primary multi fuel fuel filter. It hardens like a rock and fittings are impossible to remove, it is on the threads of the inlet bottom fitting of the booster pump too!
Reminds me of old school plumbers putty which it probably is, used on kitchen drain pipes make up fittings. rustystud wrote about that stuff once but I can't find that thread.
Anybody know what that stuff is?

 

[davidb56]

Mine looked like it had Rectorseal #5. yellow and hard. It was actually a recommended sealant decades ago for gas, oil, water, diesel, hydraulic fluid, natural gas, etc.