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MG Midget and Sprite Technical - Fuel Tank - to seal or not to seal?

The fuel tank is off and has been steam cleaned so it's back to bare metal inside and, overall, it's in pretty good shape.

Should I seal it or not?

It seems that some sealants can't cope with the current level of ethanol in petrol and break down or fall off to block fuel lines and jets. Who knows what other changes in forumlation are in the fuel pipeline just waiting to damage classic fuel systems in the next few years?

POR 15 seems to get most people's approval but,there would be the hassle of doing the job with some nasty chemicals and the risk of causing more problems by clogging the pick up strainer. At around 60 + postage per kit, that's getting close to the cost of a new MGOC tank - and the Welsh MG Centre advertises new tanks for 58.

I'm minded to stop now, give the outside a coat of stonechip and invest in an extra in line filter to catch any fresh rust particles and then keep the tank topped up to minimise the amount of tank wall exposed to the atmosphere.

Any thoughts?

Off the wall thought: When the car is spending a lot of time sitting idle in my none too dry garage, would condensation and surface rust be prevented if I filled the tank with inert gas (Welding CO2 or argon?) and sealed it with a non-vented cap?

Colin Mee

I bought a new tank when I rebuilt the frog. I had the outside powder coated and left the inside in bare metal. I just leave my tank filled up to prevent condensation.
Bob Beaumont

Its surprising that no one makes an aftermaket plastic tank to those dimensions. It couldn't be that expensive to manufacture.
Guy W

Apparently, Fertan Tapox can be used on the inside of fuel tanks...
Dave O'Neill2

Thoughts on plastic tanks Guy... I can't think of anything that has a plastic tank (I await to be corrected...) I would think it is perhaps a safety issue. If something hits a metal tank it dents or creases. You hit a plastic tank it will more likely crack and piss all the petrol out! Especially bad in a crash. Even worse with the "exposed" tank on the midget.

M Le Chevalier


Plastic fuel tanks have been used in production vehicles for a couple of decades at least
David Billington


Plastic fuel tanks have been used in many production vehicles for a couple of decades at least. IIRC the famous Ford Pinto had a metal tank and look what happened to that but somewhat from bad design leading to the puncturing of the tank in a rear end shunt.
David Billington

Malcolm, my impression is that almost all modern cars use plastic tanks. Not sure what sort of plastic though.
Guy W

I'll give you the benefit of youth on this one and accept that while you have spent your foremost years helping to ensure British classics survive, which we all applaud and encourage :) you haven't really kept up to date, have a look under your future wife's modern (if you must!). It'll have a plastic tank....
I'm with Dave (well I think I am). My first experience of a Ford CORTINA Mk3, which was sadly purchased by my younger brother in, oh let's just say the late 70's! The tank was fine but the design of the filler neck was even worse than a midget front spring hanger arrangement :) and lasted about half as long... Back then we were, like you now, learning about how to keep a car on the road on a budget (but ours was way less than yours appears to be!). Plastic, in the form of GRP, was used freely to fix rusty metal filler necks in areas where they really shouldn't have been in the first place.

back to OP...
Zinc rich primer, a flexible stone chip and a good top coat paint on the outside and use it all year so you refresh the volatile stuff on the inside :)

Best of...
M McAndrew

They make inexpensive plastic tanks in various gallon capacities.... there fuel cells,so better then a tank

Ebay is your friend, plus jegs, and summit racing

Prop and the Blackhole Midget

no need to put anything other than petrol inside the tank....
David Smith

Ha ha, no worries, thought I might be setting myself up for a flaming there! :-)

Most modern car I worked on was a Rover 25, that was metal. And my friends turn of the century Civic, because that rusted out. But they were both cars designed in the 80s.

Learn something new every day!

M Le Chevalier

P.S. Also, its not wife's car! Its mine and I let her permenantly borrow it!
M Le Chevalier

I got a alloy (9 gallon) fueltank, solves the potential rustproblem and gives a bigger radius on one tank,.
Some would say because you fill it up less frequently it runs cheaper. ;)

A de Best

With new tanks being so cheap just fit and forget. A decent coat of paint and waxoyl on the outside and it will last for years. I'm with David S on this, fuel only in the tank. The tank liners are so hit and miss and I'd only consider them on something like a car or bike where new tanks aren't available or are expensive.
john payne

This thread was discussed between 16/01/2014 and 18/01/2014

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