thread sealant?

[Csail]

Is there a product to put on threads to stop air leaks on diesel lines?

 

[Evadne]

The smug answer, as I'm sure you'll know, is that you shouldn't need anything if they're done properly. I used ptfe tape, which worked fine, but be careful not to get any bits protruding into the pipe or they'll end up in your pumps and filters.

 

[DaveS]

There is, a blue material that comes in a tube and does not set hard. I can't remember the exact name, but it's something like "Hydrolar". Last year I re-assembled all the joints on the suction side using this and it worked well.

 

[Csail]

Was it Hylomar or something?

 

[savageseadog]

It depends on what type of line and type of fitting you are talking about. Generally on the high pressure side it's metal to metal at all times and definitely no sealer. On the low pressure side BSP and NPT threads would be sealed with PTFE tape, other sealers might be OK but I use PTFE. Any other fittings would be compression fittings which are metal to metal which should't require any sealer.

 

[Stemar]

Two tricks - First, don't overtighten compression fittings, They only need to be nipped up plus a little bit, othewwise you can distort the pipe and olive and it'll never seal. The second is to use new copper washers when fitted and, again, don't overtighten. In both cases, if you didn't tighten quite enough, you can always tweak it up a bit more, but once the pipe's distorted or the thread's stripped, you're stuffed

For a get-you home repair, you can often get away with softening the old washer by heating it to cherry red (unripe cherry, ripe cherry, black cherry? I never did find out, but good 'n red works for me) and dropping it into cold water. Of course, if it gets you home, it's unlikely to start leaking next month or next year, but you'd never leave it, would you? - 'cos it's bad practice and might save you a few quid, which would never do...

 

[srp]

Definitely Hylomar universal blue - http://www.hylomar.co.uk/universalblue.htm

 

[DaveS]

That's the stuff!

 

[mithril]

I've used Hylomar for years on cars, super stuff, but dosen't it soften when exposed to diesel? If so its no good on fuel lines, it will just mask the problem for a few weeks.

 

[DaveS]

Their website (see link above) doesn't specifically mention diesel, but does say it's resistant to petroleum, kerosene and engine oil, so I would be surprised if there's a problem with diesel. No doubt someone on here will know definitely.

 

[gandy]

I just picked up a tube for £3.99 from the filling station on the way home. That'll go in the boat tool kit. We've had some Diesel leak and air problems, hopefully now fixed, but its as well to be prepared.

Even on the tube an packing it doesn't specifically say its resistant to Diesel, so I might try a little test.

 

[savageseadog]

I think the main problem with Hylomar (which I have used for car jobs) and other sealers with diesel is if there is any residue of fuel it won't bond onto the surfaces. I imagine Hylomar is OK in other respects but it wouldn't be my sealer of choice for diesel.

 

[DaveS]

I wouldn't disagree with that, and I certainly wouldn't suggest trying to put a layer of it over dubious joints as some sort of magic fixit. When I took apart all my suction side joints last year I thoroughly cleaned everything before re-assembling using a smear of Hylomar.