Mercruiser 4.3 carb weep

[Superjetjim]

Hi I have a slight leak between the two nuts on the fuel pipe as they enter the carb. Can you use a small amount of plumbers tape between these nuts to stop it or should I look elsewhere / tighten further?

 

[Rick Stephens]

Tape probably won't help with a flare fitting. I'd inspect the tubing flared end for cracks before choosing a fix.

Rick

 

[Scott Danforth]

^+1.....what he said

 

[Bondo]

Ayuh,..... Ditto,...... The fittings closest to the carb, where it screws into the carb, is pipe threads, so pipe dope is used there,......
That fittin' is a flare fittin' to the line's fitting, so no pipe dope there,.....

 

[achris]

.... Can you use a small amount of plumbers tape between these nuts to stop it ...

Urghhhhhhhh.

My pet hate! Plumber's tape/thread tape/PTFE tape, is NOT a sealant, it's a lubricant so you can tighten the fittings to the correct torque without them galling.

I swear, the next time someone says PTFE tape is for sealing, I'm going to punch the monitor!

Chris......

 

[Scott Danforth]

I swear, the next time someone says PTFE tape is for sealing, I'm going to punch the monitor!

Hey @achris teflon tape works good as a sealant......

 

[Tail_Gunner]

Carry on

 

[Grub54891]

Any flare fitting does NOT get tape or sealant. It bugs me to when I see that. If the flare has been tightend to much, it's shot. Replacing it along with the fitting it seats into is the only option.

 

[Scott06]

An item i recently found is a copper flare washer like these https://pontiactripower.com/product...or-3-8-fuel-lines?_pos=1&_sid=a7eb5f707&_ss=r

i assume they are from hvac but work great on sae flare fittings, especially when tightening in fragile carb bodies.

and @achris i would agree with mr danforth that PTFE tape makes a great sealant …especially on flare fittings ….

full disclosure drives me nuts too…

 

[Scott Danforth]

FYI, teflon tape should only be used for shower heads pre 1975 or so. Loctite has a whole line of proper thread sealants

 

[Grub54891]

Any flare fitting does NOT get tape or sealant. It bugs me to when I see that. If the flare has been tightened too much, it's shot. Replacing it along with the fitting it seats into is the only option.

This ^^. Pipe thread yes but not flares.

 

[nola mike]

Also make sure you didn't cross thread that nut, easy to do.

 

[H20Rat]

Urghhhhhhhh.

My pet hate! Plumber's tape/thread tape/PTFE tape, is NOT a sealant, it's a lubricant so you can tighten the fittings to the correct torque without them galling.

Just came in here to say that even the manufacturers call it sealant... ;-) (Seal is mentioned 14 times by the mfg, lube isn't mentioned once.)

Blue Monster™ PTFE Thread Seal Tape

Blue Monster PTFE Thread Seal Tape is a thicker, denser, general-purpose thread seal tape that comes in a monstrous 1,429

cleanfit.com

It does both. If you needed a lubricant only, there are MUCH better lubricants that would work. (a drop of 5w-30 for example...) All threads have micro cracks and defects. The material added by the tape fills those defects and seals it.

In any case, you don't use that on flared connections. At most, you use a TINY amount of paste on a flare, and then wipe essentially all of it off. Just helping to fill in those micro defects.

 

[achris]

Just came in here to say that even the manufacturers call it sealant... ;-) (Seal is mentioned 14 times by the mfg, lube isn't mentioned once.)

Blue Monster™ PTFE Thread Seal Tape

Blue Monster PTFE Thread Seal Tape is a thicker, denser, general-purpose thread seal tape that comes in a monstrous 1,429

cleanfit.com

It does both. If you needed a lubricant only, there are MUCH better lubricants that would work. (a drop of 5w-30 for example...) All threads have micro cracks and defects. The material added by the tape fills those defects and seals it.

In any case, you don't use that on flared connections. At most, you use a TINY amount of paste on a flare, and then wipe essentially all of it off. Just helping to fill in those micro defects.

They call it 'sealing tape' so morons will use more of it (and hence the companies make more money).... And TPFE as a lub needs to be used where oils and greases can't be, like food prep, high O2 environments, subsea....

And to those who say it's both, I'm yet to see a piece of TPFE tape that can stand up to any more than a few pounds of pressure. Even your house plumbing is at least 40psi... TPFE is NOT a sealing tape!

Chris...

 

[Grub54891]

An item i recently found is a copper flare washer like these https://pontiactripower.com/product...or-3-8-fuel-lines?_pos=1&_sid=a7eb5f707&_ss=r

i assume they are from hvac but work great on sae flare fittings, especially when tightening in fragile carb bodies.

and @achris i would agree with mr danforth that PTFE tape makes a great sealant …especially on flare fittings ….

full disclosure drives me nuts too…

Yet another case where replacing the line and fittings come into play. If it leaks due to wear, it needs to be replaced.

 

[achris]

FYI, teflon tape should only be used for shower heads pre 1975 or so. Loctite has a whole line of proper thread sealants

Yep, like 567... Use that a heap, especially on hydraulic fittings.

 

[Lou C]

Interesting, I replaced the mechanical fuel pump, rebuilt the carb a couple of times, replaced the steering actuator, all with flare fittings never used sealer, and never had a leak!
Here's a tip, when replacing/installing a carb, or fuel pump, thread the retaining nut on before tightening the carb/pump down fully on the engine, this gives you a bit of movement to allow the threads to get 100% lined up so you don't strip or cross thread them.

 

[Superjetjim]

All sorted thanks, mechanic tightened it up more than I felt comfortable doing

 

[Lou C]

Just remember my trick, if you are installing a carb, set it down in place on the manifold before tightening the carb bolts, just thread them on loosely and then, thread the fuel line fitting on, by hand. Then tighten with a wrench then bolt the carb down. Been doing it this way since the '70s. Same with fuel pumps, install the mounting bolts loosely to allow some movement in the steel line so you can get the threads started without cross-threading. When I remove a carb I will loosen the carb bolts first, so it can move a bit, then loosen the fuel line nut, again it prevents strain against the threads.

 

[achris]

Interesting, I replaced the mechanical fuel pump, rebuilt the carb a couple of times, replaced the steering actuator, all with flare fittings never used sealer, and never had a leak!

Flared fittings, like JIC, Swagelok and inverted flare (think power steering, fuel pumps etc) rely on the flare to seal, no the threads. The threads are they just to force the flared parts together, hence the lack of need for any sealer on the threads. That would be like throwing your fishing line onto the land to catch fish. Just

Thread sealers (like the Loctite 567) have a PTFE component as well as the sealing chemicals, hence they CAN be used as a sealer. Straight PTFE/plumbers tape is JUST PTFE, and thus IS NOT a sealer, it's a lubricate so the threads don't gall before reaching the right torque to actually seal. And it's usually tapered threads, like BSPT and NPT... Parallel threads usually have a washer or Dowty seal behind them.

Chris......