Hi All,

My fuel tank has been slowly leaking out onto the ground even after tightening up the drain hose.
Today I pulled the tank and the drain plug has stripped threads.

Any suggestions on how to fix this? Happy to put a blank plug in the hole, but how can I deal with the stripped threads?

TIA

Sounds like you'll have to try a helicoil if one exists for the thread size (not too sure what it would be), or try re-tap the thread to a different size.

A last ditched effort would be, if you know you are going to just blank it anyway, take it to a radiator repair place and they can just plug and solder it.

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-----Better is the enemy of good-----
-1976 Yellow Devil Leyland Clubman-
-1970 Morris Mini Van - Work in progress-

A helicoil wil most likely leak even if you use loctite. And a radiator repair place will probably baulk at heating a fuel tank. It is very hard to get a fuel tank clean enough for solder to take.
I would try a blank plug with a fuel resistant sealer.

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Cheers Dave.

Ben, been thinking about your problem. Dug out a broken fuel tank drain plug, the thread is 3/8 UNF, checked by screwing on a 3/8 nut. The thread doesn't seal the tank, it is sealed by the tapered point which seats against the tank fitting/seat. My guess as the seat is at the end of a "blind" hole, it does have a small hole/seat to take the taper which opens into the tank, a helicoil may be a possible solution as long as you have a plug tap to enable the thread to extend deep enough into the hole. I am also assuming your tank has a similar plug.

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Clive G
1969 Mk II Cooper S
1970 MK II Cooper S
1963 Triumph Spitfire
1982 RX-7 Series 2

I’ve used radiator repair places to do modifications to fuel tanks before - baulk free in fact and suitable for EFI. Just give them a tank that’s prepped for solder if you go down this path.

_________________
-----Better is the enemy of good-----
-1976 Yellow Devil Leyland Clubman-
-1970 Morris Mini Van - Work in progress-

I had a radiator shop weld on a new fuel neck to my tank. They should have all the gear to do them safely

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Thanks all for the suggestions.

I think I will try the helicoil route first and see how that goes, before anything more expensive
As mentioned the "seal" is not the thread but the plugs tapered end seating in the bottom of the hole, so should be ok.

A competent old school radiator shop (if there are any left!!) knows how to 'kill the fumes' in your tank before commencing any hot work if you need to go down that track.

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Pete...
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1968 Deluxe 1275
1969 Deluxe 'Scruby' 998 Waiting for a roof skin...

From memory, the original radiator plug is the same thread. You could use one of these and solder it in (using a radiator shop).
Alternativley, it is also the same thread as the front brake bleed nipples (except 850).
Fit a bleed nipple, cut it flush and solder it in.

The radiator plug is 1/8 BSPT.

If you want to seal it permanently(ish) then I reckon a 3/8 bolt covered in fuel safe gasket sealant will do it. You could even use a 3/8 grub screw, they have a tapered tip

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did I tell you that I won a trophy?