Leak from 4.0 Autobox dipstick tube connection

[ptjs1]

I just wondered if anyone had any thoughts on how I might cure an annoying minor leak from the joint of the dipstick tube to the sump of the autobox on my 1994 AJ16 Convertible?

Ever since I dropped the sump in 2016, I've had a very minor but constant leak from the tube connection to the sump. And despite disconnecting and reconnecting it a number of times, I can't seem to stop it. Has anyone else had this problem?

The surfaces on the inner flare of the tube end seem fine, as does the tapered boss of the sump. The joint seems to pull up cleanly and the nut tightens well. But I still end up with a drip. So what can I do? Is there something that I can very carefully smear on the surfaces of the pipe flare and the sump boss to help them seal (that won't get into the box fluid and congeal)?

Tks

Paul

[andypryce]

Would some PTFE tape work?

[ptjs1]

Andy,

It's not the threads on the nut that is the issue. It's the joint of the tube onto the taper of the boss in the sump which is the problem. The nut is done up very tight, in fact, trying to stop the drip and tightening the nut further, I'm concerned it might even deform the female flare in the dispstick tube.

Paul

[andypryce]

Ah yes I see. Maybe a smear of something like Fernox leak stopper then?

[ptjs1]

Hi Andy,

I've just looked that up. Seems that sort of thing might be the job.

Tks

Paul

[PaulGover]

... It's not the threads on the nut that is the issue. It's the joint of the tube onto the taper of the boss in the sump which is the problem. The nut is done up very tight, in fact, trying to stop the drip and tightening the nut further, I'm concerned it might even deform the female flare in the dispstick tube. ...

This sounds similar to leaks from power steering pipes' flared joints, which I read somewhere are usually down to fine cracks in the flared section that only open when you tighten the joint. AFAIR, the cracks were caused by overtightening, so of course the harder you try to fix it that way, the worse it gets.

If that's a correct diagnosis, the cure is a new pipe, or if you're lucky enough to have or know someone with the appropriate tool, cut the end off the pipe and make a new flare.