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LarryH57

Lwt Land Rover Fuel Tank

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The nearside fuel tank in my Lwt is weeping slightly from around the drain plug but it only drips fuel if the tank is full but stops if it gets to about 20 litres left. It's been like this for several years and still passes its MOT.  A LR engineer friend of mine said that such weeping  is due to a leak in the seem around the side of the tank and fuel leaks towards the drain plug under the underseal, rather than the leak being near the drain plug itself. I've no idea if this is true. 

I have got a replacement tank ready and painted in about four coats of printer and red oxide and two coats of hammarite, but I want to coat it with underseal like the original but have no idea of whether it will stick to paint or how it was applied in the factory. My undercoat is in a tin and soluble in petrol so I guess I could stipple it on.

As for the 20 litres of fuel I forgot was in the tank its from at least 2016, so guess its gone off, but if I introduce a bit at a time in to the Lwt it might not notice as it seems to like old 97 Ron fuel.

Edited by LarryH57

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AFAIK  , Solihull did not apply the underseal - must have been done at Ordnance Storage  ?  The underseal would have been asbestos reinforced bitumen type - so not fuel resistant.

Later Lightweights were not undersealed (probably from abt. 1980).

I would just paint with a fuel resistant machinery enamel (when through dry) , I normally apply a few coats of such as Tractol.  If you must apply black-clag - just do it at the sill where the tank is seen - any of the newer wax. based (black) underseals .

It will not be fuel migration from actual leak under underseal , there is a 'cradle' - this is where the leak tracks.

------

There are  early and late LWT tanks  (in fact Optional Cat. Aux. tanks)

Early tanks are made from  "terne steel"  similar to Rolls-Royce, quality but with a weak point , seams are all lap-construction with the top seam (near filler neck) abt. 10mm wide solder seam - a weak point that cracks (I became quite skilled on re-solder).   IIRC the bare tank is secured to the cradle with solder plugs.  I once abt. 1978 did a repair to a pin-prick leak from base of a tank in Snowdonia - 19FM65 and the tank is still fuel tight. Empty tank - I eyeballed the leak , stuck a 2p coin using Araldite and thetank still holds fuel. I should have asked the wife , I stuck my BIG hand through the filler hole , the wife just applied Fairey liquid and helped pull LoL

btw  - we are talking 'genuine' tanks here because , the later tank is more or less a copy of a Copy-tank that was on sale from 1970's that I know of.  The later gen. tank is identical other than the "X" side panel pressings are a mirror-image, or I should say the copy tank was a mirror of the original gen. tank.

So the Mk.2 tank is gas welded seams + gas welded top seam.  I would have to check to confirm but 95% certain the cradle is solder plug secured also. I think the material is just electro zinc plated , not terne that is superior anti-corrosive as it is a lead/tin mix with quite a few microns of thickness too.

The leak may be from where the threaded boss is secured. May be worth a try with a new copper washer - just in case, a copper crush type or Dowty may be better.     

If the tank were mine - I would remove , clean out and dry - then soak aerosol dye-pen (crack testing stuff) into edge of cradle (both sides + cradle hole for filler boss) - you should see the leak hole after a while  - use your intrinsically safe torch !

 

 

Edited by ruxy
spelin

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Thanks Ruxy.

I am planning to remove the old tank and clean it all off and see if it can be saved.

Incidentally I have another tank that is good to go - but it looks like it was damaged when removed because the single hole at the rear has 'broken out' of the steel support bracket - so the hole is open and edged by two turned up corners. Now people laugh when you suggest welding a petrol tank but it has been cleaned out for about 12 years so I was wondering if the bracket could be heated, the broken edges hammer flat and perhaps a large washer welded over the hole to restore it.

The damage to the rear bracket suggests the front two nuts and bolts were taken out and the tank fell out or off its supports and so ripped the rear single bolt hole!

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Before plastic tanks ,  the procedure was always to remove from car and proper steam-clean for a period.  To be honest - I just use a wall-paper stripper steam cleaner for abt. 1/2 hour.

btw ,  I have the odd tank (late type) that does seem gas seam welded , some roughness present.  This morning I had a quick look at some tate tanks and the seams could be friction/resistance welded = difficult to tell under the paint.

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Ruxy,

Have you any thoughts on fixing the tank with a broken rear attachment plate?

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I heard of people putting water in a tank before welding, not sure of success

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1 hour ago, LarryH57 said:

Ruxy,

Have you any thoughts on fixing the tank with a broken rear attachment plate?

The rear attachment spl. shoulder bolt & rubber buffer , the hole is through the cradle.  If it is just local rot. It just needs a reinforcement strip tack-welded on the underside. In fact I think a bit of 1/8" x 1" strip could be fitted loose in the inverted channel , better still you could drill & bolt it in position - if the bulk of crade back flange is  still intact. .  I recently purchased such a 1m length of black strip from B&Q , I think it was only £2 to £3.

Most welders for that external welding , would at least require the tank water washed internal, at that location that is all I would do & leave the cap off to vent.

More than local rot  (they are a mud/water trap) - a proper welded repair to replace the full back-end of cradle should be possible.

Edited by ruxy
spelin

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The bracket on the rear of the tank is just damaged by a botched removal and has no rot nor any fumes. I like the idea of drilling and bolting the metal strip as no welding would be required.

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10 hours ago, LarryH57 said:

The bracket on the rear of the tank is just damaged by a botched removal and has no rot nor any fumes. I like the idea of drilling and bolting the metal strip as no welding would be required.

In that case - you should be able to B&D it and have it stronger than originally.

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Last point; what do you all think of the fuel tank sealers by Frosts PO15 etc?

Edited by LarryH57

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I have one tank sealed with POIR15 and after 6 years it's holding up well..

The tank is filled with the highest Octane fuel I can buy.

I recommend it strongly.

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I have never actually used a slosh-tank sealant,  pros/cons I suppose,  corrosion could carry on to  'lace'  then lacking structural integrity , but the bladder if well done should hold - how to you periodically thorough examine  ?

With a normal fuel tank I understand you introduce the correct quantity for thickness and then roll it around for even coating  ??   

I suppose with a Rover Aux. tank - that should be a easy stage of the operation, I would use a old damaged tank cap (white nylon peg broken off).  Don't use a good (and £ costly cap). .   I  am not aware of any genuine Solihull or MOD written explanation about these caps.   Following a incident (military - Army) 25 + years ago. approx. there were instructions issued to convert to the latest (current) square section cap RUBBER type seal (that replaced a crumb cork seal).  My understanding is this instruction applicable just to latest design cap,  not penultimate, certainly not earlier (I am aware of at least 4 or 5 types going back to S1 tank top-fill). Differing by style of 'prongs' for retention.  Using sandwich cork composite gaskets.

Latest - cap with riveted inner plate & annular vent ring.  I sort of worked out that the spring loaded steel ball  within the brass case is in fact  a type of  "clack" valve , that prevents fuel loss in event of a roll-over. The white nylon 'peg' for years I considered some device to stop the actual filler neck tube from rattling , in fact it incorporates  a fine mesh filter (moulded with the plastic/nylon) , from memory - I think it also had another internal spring valve.  However I don't wish to type more on these matters, ISTR the only safe way to install a earlier cap sandwich material seal is to soak it in water 24 hrs. Plus.

So - you would not wish to encapsulate these safety devices within any slosh-sealer or prevent the breather cap, thus making a pressure cap (there is in fact a pressure cap, listed as a FFR vehicle item - why I don't know). Why aux. tank caps have effectively been more or less OSA - who knows  ??

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When I did my tank I just put a plastic bag over the fill tube and a hose clamp around it to keep the slosh in.

I don't inspect my tank.

If I walk into the garage and find a 100 litres of fuel on the floor I then know I have a problem.

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15 hours ago, Zuffen said:

When I did my tank I just put a plastic bag over the fill tube and a hose clamp around it to keep the slosh in.

I don't inspect my tank.

If I walk into the garage and find a 100 litres of fuel on the floor I then know I have a problem.

These aux. top-fill tanks normally hole at the floor due to corrosion trapped between the cradle, sometimes at front/rear ends due to corrosion from trapped mud near mountings.  A visual through the filler hole and you can see the start of perforation (leak location), best to get your hand in and feel for roughness - of a pin-prick.    I suppose just coat the bottom half of tank internally is sufficient.   I have had most problems with early construction tanks with cracked top solder seam.  Bakers fluid + plumbers reel solder,  you need lots of torch  heat & be fast with it , any delay and you heat & move the lap seam under.

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I had a bit more of a detailed inspection of the inside of the restored tank and there is a patch of rust about 3 cm across, which I treated with 'rust killer' solution. However, the rust has created a very slight 'indentation' on the inside of the tank (effectively thinning the rear side) and I'd like to smooth it over with some kind of epoxy filler, but would that react with the fuel?

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Adhesive makers etc.  often have a disclaimer on their user instructions.

However ,  from a first emergency repair = coin bonded with Araldite,  I have used the original 'slow-setting'  for Rover 'aux'  petrol tank repairs Araldite (Araldite "Precision" - I think it is still called  +  the equiv. by Evo-Stik (Control)  that is repositionable for 2 hours.  Some of the chemical metals are fuel resistant too , but I can't see them having any advantage for a small repair / reinforcement like this.     I would just tip the tank on end and pool some Araldite over the corroded area  &  1/4" of surrounding sound area, wait abt. 1.1/2 hours until it is tacky and try and add a bit more freshish mix (so it does not run, probably 1 hour old ) then try and create a blob over the original application to get a bit of thickness or try the coin trick.

btw. Clean / degrease with meths first (100% alcohol & dries fast)

Edited by ruxy
spelin

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I used ordinary fibreglass to repair the bottom of a Series 1 tank many years ago. It lasted, from memory, for about 5 years.

 

 

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And after 5 years did the repair still hold even if other holes appeared elsewhere?

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From memory after the five years or so the fibreglass was starting to lift off, and more pin holes had started to appear so I bought a new tank as the club had them on offer at the time. Otherwise I would have just cleaned off the old fibreglass and done it again. Easy enough to do on the flat bottom of the tank.

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