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MG TD TF 1500 - Fuel Tank Sending Unit Leak - New Issue?

OK, so I know that MG-TD fuel tank sending unit leaks are legion and well documented in the archive, which I recently searched when researching fixes to my unit. That being said, I discovered a new way for these to leak which I did not see documented so I thought I'd include it here for posterity.

On mine it started to leak because the gasoline had delaminated the clear-coat on the paint on the tank. The DPO had the tank painted and they painted the entire fuel sending unit gasket-seating area as well, then they applied sealant, a gasket and the unit (with slotted hex-head screws which I assume are original equipment). Well, over time it developed a leak which became quite bad after the last fill-up, to the point where I simily had to repair it. After I drained the tank and began to remove the sender I noted that the clear-coat had separated from the color coat around the outside of the sender and that the space in between was filled with pools of petrol. As I examined the gasket area I found the same thing - the clear-coat peeled right off and the gasket and sealant seemed to be dry and hard - i.e. it had not leaked there, but instead between the coats of paint - clear and color.

My solution was to use a razor blade to carefully remove all the paint from the gasket sealing surface, sand down the surface so all traces of paint were removed and so that the surface was 'keyed' for the gasket adhesive, then apply Permatex (hardening type) to both the sender and tank surfaces, wait for it to set up a bit, then install the gasket and sender. I'll leave the tank dry for a few days to let the sealant set up nicely, then fill the tank and check for leaks. Hopefully this will solve my problems.
Kevin McLemore

Oh, and I should note, I also had to repair the sender itself. The small grounding wire that connects the rotating armature to the case had broken in mid-span between the armature and the grounding point (the terminal pass-through area) so it required some delicate resoldering. Testing with a meter showed the fix was effective, so I managed to save myself a few quid.
Kevin McLemore

I would use the Abingdon Spares gasket kit with the green gaskets for the back plate, terminal, and unit to tank. The hex screws not original but later repros. Originals were just regular cheese head slotted, but it shouldn't matter. George
George Butz

Cheese head? I had not heard that term before. I guess I am not in the know on fasteners but a Google search and a look at Grainger's site supports this term.

It does sort of resemble a block of cheddar.

Learn something new everyday.
Christopher Couper

Kevin, the slotted hex-head screws would not be OEM. The issue is whether, or not, the screws are the original 3BA thread and not 8-32. The captive nuts in the fuel tank are 3BA. I'm with George on the A/S kit. Bud
Bud Krueger

Thanks, guys. Yeah, it's entirely possible that this is a replacement tank as it appears to be in very good condition. As such, the screws are probably new as well, matching to the new tank... in any event they screw in nicely, so the threads clearly match.

I definitely hear you on the gaskets. Thanks! The ones I took off had 'Nissan' stamped on them - obviously they were cardboard which had been cut out of a Nissan parts box and the labeling was from the container. Surprisingly, they didn't leak, though!
Kevin McLemore

This thread was discussed on 17/08/2014

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