DJE
Well-Known Member
Can I use PTFE tape to seal threaded joints on diesel pipes? Or do I need something special?
Thread Sealant on Fuel Pipes.
- Thread starter DJE
- Start date
AllanG
Well-Known Member
If the pipe olives are in good condition, which they should be, then you shouldn't use any form of thread sealant on fuel pipes.
macd
Well-Known Member
As AllanG wrote. PTFE tape is a bad idea, anyway, as shreds of the tape are apt to get carried along the pipes to where they may block the flow.
DJE
Well-Known Member
I haven't dismantled the old ones yet but I don't think they have olives. These are the connections to the fuel tank and shut-off valves. They look like threaded elbows, ball valves, and hose tails. They connect to what look like threaded fittings on the top of the tank and flexible hoses that lead to the engine. A couple of the joints are a bit loose.
macd
Well-Known Member
If you're stuck with worn existing fittings which can't easily be replaced, then maybe you will need some sort of liquid sealant. This should be specifically rated for use with diesel fuel. Loctite 577 is good for the job, but there are plenty of others.
Ideally, compression fittings shouldn't need anything.
Ideally, compression fittings shouldn't need anything.
oldharry
Well-Known Member
There ought to be some means of sealing the joint other than just the thread. Common types are copper or fibre washers, olives or flared ends like those found on brake pipes in the car. Although the connectors are on low pressure parts of the system diesel is highly penetrative and will leak if there isn't a proper seal. I have used PTFE on diesel pipes but with very limited success. Bits break off and cause problems downstream so I don't use it nowadays for diesel, as suggested above. PTFE doesn't seem to work at all well in diesel. Fine elsewhere though!
ip485
Well-Known Member
FWIW Loctite 577 as mentioned above was specifically required when fitting a tap into the bottom of my water seperator. It hasnt leaked!
Pete735
Well-Known Member
Another one for Loctite 577, I have used it on all threaded diesel joints and never had a problem. Not cheap by the way.
RichardS
N/A
I'm not sure what type of connection we're talking about.
If they are tapered fittings then PTFE or a sealant will be required. If they are compression fittings with an olive or a flared end or a washer or an O-ring, then no PTFE or sealant should be required.
Richard
If they are tapered fittings then PTFE or a sealant will be required. If they are compression fittings with an olive or a flared end or a washer or an O-ring, then no PTFE or sealant should be required.
Richard
DJE
Well-Known Member
They are threaded fittings, not sure if they are parallel of tapered threads, but currently sealed with a mixture of PTFE tape and some sort of fibrous cord. And loose enough to rotate with one finger so I'm surprised that they aren't letting in a lot of air.
RichardS
N/A
They sound like tapered fittings to me, probably BSPT, but it's difficult to be sure until you have stripped them down and can examine the threads.
Richard
Appledore
Well-Known Member
On a similar thread (no pun intended!!) some time ago, someone recommended Hylomar gasket sealant. I bought a tube for about £6 from the usual site and have used it on various joints on my engine fuel system, including taper threads. So far no leaks and no problems.
paulajayne
Well-Known Member
PTFE on threaded pipe is fine for Diesel - be carefully applying it so as not to go over the end of the pipe.
Do not use PTFE or any other jointing compound on olive fittings.
PTFE info here:-
https://www.calpaclab.com/teflon-ptfe-compatibility/
Do not use PTFE or any other jointing compound on olive fittings.
PTFE info here:-
https://www.calpaclab.com/teflon-ptfe-compatibility/
superheat6k
Well-Known Member
I use the thicker version of PTFE a double wrap on pre-used olives, with the tape cut square with scissors, with a smear of 577. Works for me.
alan_d
Well-Known Member
I haven't used it myself (yet), but this stuff from Toolstation specifically mentions it is suitable for diesel. https://www.toolstation.com/shop/Pl...les/sd2711/Tru+Blu+Pipe+Thread+Sealant/p40236
I am planning on using it on BSPT fittings for LPG.
I am planning on using it on BSPT fittings for LPG.
oldharry
Well-Known Member
Diesel graded 'excellent'. Hmmm. Have they ever actually used it on a diesel line? I have. Thats why I dont any more. Works brilliantly everywhere else. I'm not a chemist, so i dont know why, but I have very rarely been able to get it to seal diesels. Oil lines, water pipes, gas pipes, even petrol - yes wouldnt use anything else, but diesel? No thanks. Just saying after years of disappointments.