Help! Fuel filter elbow fitting leaking?

[jawn101]

Hey guys. I had the extraordinary Clint ( #1768 ) over this past weekend to help me with my VOD rebuild. It went really really well with the exception of two busted bolts in the Y-pipe, which we cleared up pretty easily. Anyway, the last remaining problem is a leak in the new fuel filter. I have removed and replaced the thing 3 times already - the first, major leak was an improperly installed banjo bolt in the output hole (part of the rebuild was new stainless fuel lines from Hervey, and the new feed line needed a new bolt)

But now the elbow joint is leaking. It's a steady leak coming from the end where the cone fitting on the hard line fits into the elbow that screws into the filter. It wasn't leaking before we changed out the filter. I cleaned the threads on the elbow joint thoroughly, but because the nut can't come off the hard line, I didn't clean those better than a simple wipedown with a cloth. I have tightened the nut onto the elbow as hard as I possibly can with an 18mm on the elbow and a 19mm on the nut. I don't think it can go any tighter.

What should I look for? Has anyone else had this? I know I can replace the elbow fitting if absolutely necessary, but what do I do if the end of the hard line has somehow become damaged? Help!

Pictures (linked to John Spangler's blog, all credit to him for these - I can't get a camera under there with all this gas everywhere) are below

http://www.johnspangler.com/DMC/fuelfilter03.jpg - elbow joint in question
http://www.johnspangler.com/DMC/fuelfilter08.jpg - view of the cone end of the hard line where the leak is happening

[David T]

Make sure it is lined up straight when you are screwing it together. You can CAREFULLY wrap a LITTLE bit of teflon tape on it before you put it together being careful not to cover the end.
David Teitelbaum

[jawn101]

Make sure it is lined up straight when you are screwing it together. You can CAREFULLY wrap a LITTLE bit of teflon tape on it before you put it together being careful not to cover the end.
David Teitelbaum

I thought of the teflon tape too, but I did a little poking around and the general opinion of the internet masses is that teflon tape and gasoline lines don't mix. Thus, I didn't try it... but if it's the difference between a running and a fuel-hemorrhaging car I may not have a choice :)

[sean]

You can CAREFULLY wrap a LITTLE bit of teflon tape on it before you put it together being careful not to cover the end.

+1 on this, I do it every time just in case.

[DMCMW Dave]

+2.

I don't know where that would have come from, on the DeLorean most of the fuel lines ARE Teflon. I suppose the worry is that if you are sloppy any shards of teflon make there way into the fuel distributor Bad Things Will Happen.

[jawn101]

+2.

I don't know where that would have come from, on the DeLorean most of the fuel lines ARE Teflon. I suppose the worry is that if you are sloppy any shards of teflon make there way into the fuel distributor Bad Things Will Happen.

That did seem to be the worry... my counterpoint to that (in my head) was that this is the best possible place for those shards to happen if they are going to - their first stop would be the filter, which should easily catch something that large. But, I'm not usually sloppy - so I will give it a try! David T heavily emphasized the "little" in "little bit" of tape... are we talking a single wrap? two?

Thanks guys!

[DMCMW Dave]

Once around but enough that it stays in place. Stay away from the open end, and you are correct in that particular application the filter will stop it.

Don't put any on the banjo bolt, it won't help anyway as the seal is the crush washer.

[sean]

... are we talking a single wrap? two?
I usually go 2-3ish wraps.

[jawn101]

I usually go 2-3ish wraps.

Sounds like a plan! I guess I was crazy lucky that the previous filter wasn't leaking :) I will wrap the line tomorrow evening and see how it goes. I will post my results, because if it works there should be a video of the first startup after the maintenance :)

[opethmike]

I went without Teflon tape when I changed my filter recently. It promptly leaked, so I added three wraps of tape. Dry as a whistle!

[Mark D]

+1 on the teflon tape... I think they make a yellow version that is more resistant to petroleum products if that is your concern.

The threads are tapered pipe threads, so it should self seal. Just make sure you're not cross threading though or you could rip the threads out of the aluminum filter housing.

Don't be afraid to crank it down tight though as long as you're careful to not twist the metal hard line.

[jawn101]

I went without Teflon tape when I changed my filter recently. It promptly leaked, so I added three wraps of tape. Dry as a whistle!

With all the support for the Teflon tape idea, I am starting to wish I'd just gone with my instinct in the first place rather than spending 2 days researching and second-guessing :)

I will definitely report back!

[David T]

Many people overuse teflon tape. It works on tapered, threaded fittings and compression type fittings. It is not affected by solvents and gasoline. As pointed out the big danger in using it is getting shards of it into the system you are trying to seal. It is not a good idea to use it in any recirculating system like a hydraulic system. I used to use it everywhere but I find Pipe Dope is just as good in most plumbing applications, just a little messier. They even make Pipe Dope with pieces of cut-up teflon mixed in. Too much tape and you have trouble starting threads and much more chance of unraveling it and getting shards inside. I have even see where teflon tape was wrapped and covered AND SEALED fittings so you must really be aware of what you are doing and inspect before assembly. The less the better but you do have to wrap enough so it stays in place. The thinner stuff seems to stretch and stick to itself better but most places seem to only have the thicker stuff these days. They also make thread sealer in tubes and for some applications it is better.
David Teitelbaum

[cdrusn]

+1 on this, I do it every time just in case.



I just fixed the same problem with mine. Teflon tape on the threads allows the hard pipe nut to tighten a little bit more. The comment about not mixing teflon tape and gas doesn't fly, once the nut is tightened the gas will never touch the tape anyway. Use a big heavy crescent wrench to hold the filter elbow from bending and don't be afraid to put some weight behind the tightening wrench.

[jawn101]

Yep - a couple wraps of tape and a really, really hard crank on the nut got it all shored up. It had an extra 1/4 turn in it that I wasn't accomplishing due to the tight space, but I found a good angle and got it tightened up. Thanks for the tips!

[sean]

Yep - a couple wraps of tape and a really, really hard crank on the nut got it all shored up. It had an extra 1/4 turn in it that I wasn't accomplishing due to the tight space, but I found a good angle and got it tightened up. Thanks for the tips!

Excellent! Glad things worked out.

[Tillsy]

I am having a similar difficulty. I used the gas rated (yellow) tape for the top of the elbow fitting to the filter (visible in this picture), but not on the hard line end.

Hard to see in this picture, it does not drip or get wet as such, but the first half centimetre gets a sort of vapour wet look to it. I can rub it a few times to get rid of it and it vaporises back a few seconds late - but again not actually wet.

This is while I was pressurising the system for 15 minutes (just being annulling sure) and, with plenty of ventilation, starting her up and running for 10 minutes anyway. Never builds up a single drip or gets wet as such, just this vaporised dampness.

Would teflon tape on this join correct this?

[Bitsyncmaster]

I am having a similar difficulty. I used the gas rated (yellow) tape for the top of the elbow fitting to the filter (visible in this picture), but not on the hard line end.

Hard to see in this picture, it does not drip or get wet as such, but the first half centimetre gets a sort of vapour wet look to it. I can rub it a few times to get rid of it and it vaporises back a few seconds late - but again not actually wet.

This is while I was pressurising the system for 15 minutes (just being annulling sure) and, with plenty of ventilation, starting her up and running for 10 minutes anyway. Never builds up a single drip or gets wet as such, just this vaporised dampness.

Would teflon tape on this join correct this?

Just tighten the hard line end a little more. You don't put sealer or tape on flared or compression fittings. Yellow tape is rated for LP gas connections. You don't really need it for gasoline but it will work fine it's just thicker.

[Tillsy]

Just tighten the hard line end a little more. You don't put sealer or tape on flared or compression fittings. Yellow tape is rated for LP gas connections. You don't really need it for gasoline but it will work fine it's just thicker.
I couldn't for the life of me get it to budge a millimetre more so have taken it off, applied a small amount of tape (white though, while working in the tight space I dropped my roll of yellow straight into the bucket catching the petrol!), and refitted. Exactly per jawn101's experience I found I got it that little bit tighter, perhaps the tape made that a little easier, and seems to be good now!

[Bitsyncmaster]

I couldn't for the life of me get it to budge a millimetre more so have taken it off, applied a small amount of tape (white though, while working in the tight space I dropped my roll of yellow straight into the bucket catching the petrol!), and refitted. Exactly per jawn101's experience I found I got it that little bit tighter, perhaps the tape made that a little easier, and seems to be good now!

The tape on the treads let you put more force on the joint. You may have had some burr on the threads somewhere. Always check the mating joints for a good looking finish. Sometimes you can just sand them a little if they are scratched.

[jawn101]

Amazing that the tiniest movement of that nut is the difference between leaking and sealed, isn't it? No margin at all. Glad you got it working!