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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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Old 07-11-2009
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Dope on threads?

I am rebuilding the water pump on my Yanmar. Do I need to put thread dope/tape on the threads from the water hoses that go into the pump? I didn't see any when I took it apart.
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Old 07-11-2009
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Quote:
Originally Posted by L124C View Post
I am rebuilding the water pump on my Yanmar. Do I need to put thread dope/tape on the threads from the water hoses that go into the pump? I didn't see any when I took it apart.
You mean the hose barbs that screw into the pump body and to which the hoses are clamped, I assume. I'd use Teflon plumber's tape, were I doing it.

Jim
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Old 07-11-2009
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Yes..

I use both Teflon tape and Teflon paste pipe dope. First wrap the Teflon tape on the male threads then apply some dope. Never apply dope to anything but the male threads. This is a method many excellent pipe fitters use and it yields a much higher success rate than one or the other alone.. I like Hercules Real-Tuff as a pipe dope..

Tape:

Tape + Dope:
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Old 07-11-2009
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That's dope, Dogg.
Very nice photos.
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Old 02-21-2010
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I prefer to use "loctite" blue, tends to also resist vibration better than teflon tape and can be used for any medium, fuel, raw water ,coolant etc.
Hope this helps,
Dumah, Halifax, NS
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Old 02-23-2010
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Marine Sail,
That's an interesting idea. Do you have any stastics?
Even so, I might have to try it.

Dumah, I would think one would have to wait for the loctite to cure before running fluid through the fitting. Not sure about the pipe dope, but it's not an issue with the tape. I do know the pipe dope sets fairly hard, so I'd be careful on what I used it for.
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Old 02-23-2010
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Originally Posted by elkscout View Post
Marine Sail,
That's an interesting idea. Do you have any stastics?
Even so, I might have to try it.

Dumah, I would think one would have to wait for the loctite to cure before running fluid through the fitting. Not sure about the pipe dope, but it's not an issue with the tape. I do know the pipe dope sets fairly hard, so I'd be careful on what I used it for.

No stats but I worked in the hydronics industry for years as a manufacturers rep and sold a bunch of different "dopes".

The good pipe fitters, on nearly all the high pressure industrial jobs, and the good residential pipe fitters mostly all used both tape and dope. Over the years I saw thousands of pipe leaks, only a very small percentage, perhaps less than 1% of all the leaks I saw, were with both tape and dope. In many industrial and residential plumbing systems using black pipe the joints self seal when they rust, still a weak spot. In industrial applications for processing where stainless pipe is used they won't self seal.

My brothers boiler has no less than 8-10 joint leaks, only dope was used (Rectorseal). When I installed the boiler in my house I used Real-Tuff and tape. There were no leaks. NPT to NPT fittings do not need a glue as they are tapered threads meant to be held together by friction. If you think boats vibrate you have probably never been to a commercial plant running 200 HP high pressure steam boilers..

The dope/tape only act as a crevice filler and lubricant to get the threads properly mated. During the tightening the tape and dope will fill in any imperfections along the thread path preventing liquids from migrating though the threads.

In an ideal world the threads should self seal, that is the intent, but tap & die machines get dull, tolerances change slightly from manufacturer to manufacturer and people often don't clean the threads before application to remove residual milling crud..

Real-Tuff does not harden, as it is nothing more than specialized PTFE paste. It also has no harsh petrochemicals, like many thread sealants, in it so it's safe for most all plastics & rubbers. I have been using it in marine applications since the mid to late 80's, usually 80% of the time, with teflon tape, with not one leak.


From Hercules Chemical:

"Multi-purpose heavy duty, white, PTFE paste thread sealant for use on Aluminum, Black Iron, Brass, Copper, Glass, Monel, Natural Rubber, Plastic (P.E.,Reinforced), PVC, ABS, CPVC, Stainless Steel, Synthetic Rubber (Butyl, Neoprene).

Contains a unique system of fine grain PTFE particles specifically designed to fill cracks and tiny thread imperfections. Leak free joints can be tested and put into service at once. Real-Tuff holds tight against expansion, contraction and vibration, is non-separating, will not run or drip from joints, contains no lead. Non-hardening lubricating formula permits low torque make-up and easy disassembly without galling or stripping threads. Real-Tuff withstands temperatures from -200°F to +550°F, and provides leak-proof hydraulic
resistance to 12,000 psi. Withstands gas pressure up to 2,600 psi. Real-Tuff is non-flammable and contains no heavy metals or volatile solvents and is applied easily with a natural bristle brush, even at temperatures as low
as -25°F."


Real Tuff can be used on lines carrying:

Acids-Concentrated
Acids-Dilute
Air Compressed (Gaseous)
Alcohols
Aliphatic Solvents
Ammonia Anhydrous
Ammonia Gaseous
Ammonia Liquefied
Aromatic Solvents
Benzene
Brine
Butane Gas
Carbon Dioxide
Carbon Tetrachloride
Castor Oils
Caustic Alkalies (concentrated)
Caustic Alkalies (dilute)
Coal Gas
Coal Tar Naptha
Cutting Oils
Diesel Fuel Oil
Dry Cleaning Fluids
Ethylene Glycol
Fatty Acid (liquid)
Freons (all)
Gasohol
Gasoline
Glycerine
Heating Oils
Helium Gaseous
Hydraulic Oils
Hydrogen
Inert Gases
Jet Fuel
Kerosene
Ketones
Liquefied Pet. Gases
Lubricating Oils
Manufactured Gases
Mineral Oils
Natural Gas
Nitrogen Gaseous
Petroleum Solvents
Propane
Propylene Glycol
Soap Liquid
Sugar Liquid
Steam
Toluene
Tri-Chloro-Ethylene
Vegetable Oils
Water (cold & hot)
Water Gas
Xylene

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Last edited by Maine Sail; 02-23-2010 at 07:45 AM.
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Old 02-23-2010
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well Marine Sail,
It looks like you've covered all the bases. Thanks so much for the reply.
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