Fuel line joints

[Keith-i]

I've been suffering a small amount of air in the fuel feed to my engine for a little while and decided to remake some of the joints that may be suspect when under suction. Is there a 'best practice' method of achieving the valve connections in the photo. At the moment the threaded joints are sealed with Loctite 577 but I have a small weep from the 3/8" BSP hydraulic fitting on the right hand side which is the supply from the tank.

 

[RichardS]

It looks like a compression fitting so no sealant should be required and possibly won't make any difference anyway. If it doesn't seal when you nip it up tight then it suggests that something is wrong with the mating surfaces ..... scoring or dirt.

Richard

 

[PetiteFleur]

In theory you should not need any sealant on a fitting like that. You could just try tightening the fitting but I expect you've already done that. Perhaps replace the tubing from the tank?

 

[Lon nan Gruagach]

I've been suffering a small amount of air in the fuel feed to my engine for a little while and decided to remake some of the joints that may be suspect when under suction. Is there a 'best practice' method of achieving the valve connections in the photo. At the moment the threaded joints are sealed with Loctite 577 but I have a small weep from the 3/8" BSP hydraulic fitting on the right hand side which is the supply from the tank.

View attachment 72634

Theres a male/male barrel in that connection, isnt there? You might have luck with a new one.

 

[oldharry]

+1 That type of joint should be self sealing. If not there's something wrong, usually damaged facing where it makes contact. It takes very little to break the seal, the mating surfaces have to be completely smooth to seal properly. Simply over tightening the joint to make its work further compunds the problem by causing further damage. Using a sealer rarely seems to work, its needs to have full metal to metal contact throughout.

 

[Keith-i]

Theres a male/male barrel in that connection, isnt there? You might have luck with a new one.

As it happens, it is a new male/male barrel that I’ve used. I will need to undo it and take a closer look.

Are such hydraulic fittings appropriate for diesel fuel feeds in a boat or is that a more reliable alternative?

 

[Daverw]

As said they work by metal to metal contact so suitable for most fluids and gasses. It’s the flexible hose material that changes with use

 

[lw395]

Check you don't have a mixture of BSP and merkin threads/fittings?
I've been through this with an oil cooler years back.

 

[Malish]

personally I would move to a hose tail on the ball valve and a decent fuel pipe clamp

 

[freespiritdavid]

Put some tape around the suspect joint and test again to check it is the problem. Personally I would have sleeved soft copper pipe and use this jointed into any ball valve. Minimum joints is always better.......... works for me.