Fuel tank bottom plug leak

I have a bit of a conundrum . I noticed a slight leak from the fuel tank plug in the bottom of the tank. Presumably the gasket failed and probably time to replace the plug anyway.

However using a breaker bar and socket just rounded off the hex, and vice grips didn’t hold.

I’m considering a pipe wrench to grab the outer diameter, but concerned with damaging the tank.

Alternative is to try to use a sealant to address the leak while saving up for a new fuel tank.

This is the plug I’m talking about
https://xks.com/i-7081859-jaguar-xks-and-early-sedan-fuel-filter-co-990.html?ref=search:https%3A%2F%2Fxks.com%2Fsearch.html%3Fq%3DFuel%2Btank%2Bplug

Thoughts?

I’m in the exact same boat as you in regards to this problem. I’m told I may have to cut/ drill it out as the female nut assembly this plug is attached to is soldered to the fuel tank. So giving a good yank on it with a pipe wrench could tear it loose. Then you’re cursed with not only obtaining a new plug, but also finding a radiator or welding shop willing to solder back in the female nut. Like you, I’ll be watching this thread over the next week or so for replies.

If it were me I would try J-B Weld epoxy first. It’s available at auto parts stores. They even make a kneadable putty which you could push into the leak. You will want to clean/degrease the area with acetone or similar. Remember you are dealing with gasoline so be careful. If that doesn’t work go to plan B

Pat H

This job would be easier if you take the tank out.


Then the pipe wrench might work, and if it isn’t working you can see to stop before you do too much damage to the spout.
The operative plan is to wreck the easily replaced plug to save the hard to replace tank spout.
If you have the tank well drained and aired out, with the sending unit removed, blowing compressed air through it for awhile, so you are sure it is really dry inside, with no residual fuel vapors, you can try a propane torch on it, moving around the outside of the spout, i.e. to expand the internal threaded part. Then try the pipe wrench again.
Obviously this method is only for people who know how to tell if the tank is dry and can handle a torch.
If you’re not, take it to a body shop or radiator shop or plumber and this is what they will do.

Well now I’m perplexed… Maybe I’m talking about a different feature than I thought I was.
There’s no “spout” in the area I’m talking about. It’s basically in the center of the bottom of the tank, in a large flat area. What you’re showing looks near the corner of the tank, and I’m really not picturing where that is.

Just so we’re all on the same page, the plug I’m trying to remove is in the hole circled in this picture (bottom view of tank, picture borrowed from xks.com XK-140 fuel tank listing)

tank

Sorry to cause confusion; my picture is of my Mark V tank, but the drain plug is the same as later and earlier models, as is the internally threaded fitting brazed to the tank.

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Thanks, that makes more sense. I was really confused for a moment!

On my car the plug is pretty easily accessed, but as stated I’m concerned with breaking something.

I’m inclined to just try to seal it up with something to get it back on the road for now (been over a year undergoing carb rebuild and a few other odds and ends, which is when I noticed the tank leak).

May see what the local auto store/Amazon etc have, preferably something that I can remove in the future if I get the opportunity to remove the tank and do a permanent fix.

When I purchased my XK120, the fuel tank plug was stuck, but I managed to remove it with a very large pipe wrench. I used a floor jack to hold the pipe wrench jaws tightly against the bottom of the tank and plug while I braced my feet against a rear wheel to get leverage.

The culprit in these stuck fuel tank plugs is the gasket between the plug and tank. Some of the gaskets are made of a soft rubbery material that tend to weld the plug to the tank after many years. The better gaskets are made of hard red fiber like the ones used in our SU carbs. The red fiber gaskets will allow easy removal and reuse well into the future.

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No issues breaking the brazing/welding with that method?

Mine is the original tank, and I had no problems. If the bottom of the tank is badly corroded, you might tear out the female threads.

Before I did this, I disconnected the flexible fuel line in the engine compartment, put a hose from the flexible fuel line to a jerry can, energized the SU fuel pump, and drained the tank.

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Yes my tank has been drained using basically the same method, and further drained by removing the fuel outlet from the tank (adding a shutoff valve to allow future fuel filter/rubber hose changes without needing immediate thumb application!)

So maybe back to having the big wrench option… Just don’t want to tear the bottom of the tank out!

Hi Brandon,
I took the tank out, dried the tank and then heated the ring to loosen it. I kept heating it until the solder melted and the entire assembly came out. I then clamped the hex in a vise and heated the ring red hot until the glue the DPO had used let loose and I was able to separate the parts. It was then easy to clean the threads and solder the ring back onto the tank.

Two takeaways: It’s easier to work on the bench, and don’t you be the DPO who uses epoxy to keep it from leaking.

i would agree with mike. it is easy to remove tank and take it to professional for cleaning and repair.there is at least 1/2 gallon of liquid in the bottom of that tank which is a real bomb. i don’t want to be pedantic but you already know that and i have had to do the accident investigation and burn ward interviews.

Well I was going to look for a different option, some sort of silicone seal type material that would be fuel resistant, but could be removed later if needed; never intended as a truly permanent fix.
Something like this

My big problem is time. The 140 has sat since last April when I started rebuilding carburetors. If I drop the tank it will probably be another year if not more before I get around to doing anything with it. Between a 4 year old, one year old, full time job, house upkeep, 6 other vehicles, 3 trailers, miscellaneous other endeavors, this usually drops to the bottom of the list… the carbs were rebuilt literally “ten minutes at a time” over the course of months, after the kids went to bed on week nights.

I’ve been “working on” this plug for something like 4 months at this point, again 5-10 minutes at a time around midnight…

A lot has changed since working on this car when I was in high school!!

If I were to remove the tank it would most likely be to just replace it with a new one, but time and $$ are never in plentiful supply!

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I’ve also tried the vice grips and large pipe wrench. As others have mentioned, the large pipe wrench was starting to distort the bottom of the tank. I finally gave up and took it to a shop which specializes in repairing and resealing old car and motorcycle tanks. When I went to pick it up he had done a wonderful job coating the tank interior - but he still couldn’t remove the plug!!! I pointed out to him that he had probably sealed up the screen in the drain plug and that the pickup tube now wouldn’t draw petrol.

Anyway, I brought the tank home, filed down the raised hex section on the damaged plug to the next smaller socket size and then easily removed the plug with an electric impact wrench. The plug quickly loosened with no damage or distortion to the bottom of the tank, unlike when I attempted to use the pipe wrench.

Seems strange that an impact would do less damage than normal torque.
I’m still mulling over what to do here. Filing down the plug seems quite tedious but maybe not a terrible idea…

Has anyone had any luck using a bolt extractor? For some reason I completely forgot these existed… pretty sure I even have a set. Either with breaker bar or impact…

This isn’t what I have, but an example of what I’m talking about…

the extractors may or may not work…worth a try…they have sharp inside edges that grab the nut/bolt head. breaker bar has leverage advantage, is controllable…but may be too much leverage on attached parts that you don’t want to damage, …and does not have the “vibration” of impact that sometimes aids removal…but…the impact is less controllable…and may vibrate other things to the point of damage as well…so it seems what I have said is of no help or value…:slight_smile:
Nick

Funny how that is…I think there is part of us with these cars always with high school mind and heart.
But 6 cars? Mamma mia…only in America.

Good advice above, but if it were me…

Cheap hand pump siphon from amazon with tube hose at either end.
Disconnect tank connections, plug one going to carbs of course.
Use car pump to pump out gas.
Siphon remaining fuel. Disconnect and plug all connections.
Fill tank with water…pump it out.
Allow dry couple days.
Fill with water again with shot glass or 2 of oxalic acid. Allow sit a day or so to attack corrosion.
Give it a go with propane torch after spraying down exterior everywhere with water to displace any gas or fumes.

Propane torch $5 walmart
Hand pump $10
Oxalic acid $8-10 e b a y

You really need to try shock it off with inpact tools, but as archimedes said, give me a long enough lever and i can move the world.

Don’t be afraid to heat it for a while. Be focused though.

If no, pump out water and pour a jug or 2 of marvel mystery oil in there and let soak a week or whatever and repeat. It is very good against rust.
Also evaporust.
It should come…

Also instead of hand pump there is also small submersible pump on e b a y…cheap.

Best of luck.

PS:

Hi Brandon,

if you were to apply a torch to a tank, then in addition to the above steps, I would also fill the tank with CO2. An old CO2 fire extinguisher would do it, or possibly an inert shield gas? (don’t use a semi-inert)

Regards,

Jon Vains