Petrol Tank Removal (and hopefully repair)

[GeoffSmith]

I like Loctite. On page 34, 406 with 770 activator look good - just don't look at the price.

Indeed - the trick here of course being the 770 - not an activator but a polyolefin primer.

Comes back to the acknowledged problem of getting a surface key to the HDPE...

I happened to find some (normal viscosity) and I've been fixing all those 'difficult to stick' plastic things around the house. I'm really impressed but would probably recommend going for the medium viscosity stuff for the fuel tank.

[Gordon]

Here's what is hopefully a stupid question, but I find myself unsure...

The tank was originally secured with two M10x50mm 8.8 bolts, into weldnuts on the tankstraps, with M10 halfnuts added as "locknuts"

I was intending to replace with M10x50mm A2 Stainless blots , penny washer and A2 Stainless nyloc locknut...

Question being, the M10 A2 Nyloc nuts I've got are 10mm thick - 3mm of that is the nylock ring, so I'm only looking at 7mm worth of thread in the nut - far less than the original weldnut & halfnut-locknut

Is that enough to hold a tank full of fuel under usual conditions? - I'm guessing it is, but I'd like a 2nd opinion! lol
Gordon

(I'm sure it must be, as the strap would pull over the nut, way before the nut would strip??!)

[GeoffSmith]

I would think so Gordon.

[RayD]

I’m sure Geoff is right Gordon,

Going from memory of seeing mine the strap isn’t tight up … which would be the reason for them choosing to use an added locknut.

An ordinary steel 10mm Nyloc nut is 11.5mm deep, with, as you say, about 3mm of locking ring.

I’d rarely go out of my way to use stainless bolts.

If there’s enough thread and you wanted it to more closely resemble the original you could cut the locking ring section off one nut and put it on first … then lock a Nyloc nut to that.

They wouldn’t have time in the factory but if I were doing it I could imagine tightening it up – checking the gap – slackening it off and inserting a spacer in order to be able to tighten the bolt properly.

Ray

[Gordon]

They wouldn’t have time in the factory but if I were doing it I could imagine tightening it up – checking the gap – slackening it off and inserting a spacer in order to be able to tighten the bolt properly.

Ray

Tank has now been refitted; giving me a few observations that may be worth sharing...

Firstly, as Ray pointed out - the tank straps do not necessarily need tightening fully back to the body...
My inboard strap went right back to the body without any undue load on the tank -
The outboard strap however was already tight with still 10mm of thread to go (now spaced) - this does lead me to wonder though...
As original fitment, the strap was tightened right down to the body - this would have been straining the outboard side of the tank somewhat, and possibily lead to the cracks around the filler neck (being a naturally weak spot in the tank?)

When refitting the filler hose from the filler neck to the tank, I didnt feel that that was the source of any preload on the tank neck, making me think that this stress has come from somewhere else?

Secondly; the various pipe clips on the balance pipe atop the tank were quite rusty and tired, so I took this opportunity to replace them;
If you do, pay close attention on refitting so as not to leave any sharp edges on pipe clips where they may potentially rub against the other pipes in that area! - main fuel feed specifically! I'll add a picture of what I'm talking about when I get a moment. It's quite tight in there!

Finally, the tank being off was an ideal chance to sort out the drain for the fuel filler cap! it had been blocked since I had the car, and the tank being out of the way is the only chance to replace it (or in my case clear it through).

Gordon

[Gordon]

Oh, and when you put the two pressure fittings back onto the pump;

Fuel return (red) first!

If you put the white one (feed) on first - you will curse...

[RayD]

.... The outboard strap however was already tight with still 10mm of thread to go (now spaced) - this does lead me to wonder though...
As original fitment, the strap was tightened right down to the body - this would have been straining the outboard side of the tank somewhat, and possibily lead to the cracks around the filler neck (being a naturally weak spot in the tank?)

Glad you got it sorted Gordon,

It’s an interesting point about neck failing and the strap being fully tightened … we’ll have to see if other failures have the same combination.

It makes you wonder if the ones that failed did so quite quickly after production … rather than waiting 20 years I mean?

Ray

[pjw12]

Is there anyway of getting at the filler neck without complete tank removal?

[Gordon]

No

[pjw12]

bugger!

[Gordon]

bugger!

bugger indeed!

And it's a two person job aswell, as the bolts retaining the tank straps are a PITA.

On the up side, I'm very happy with my repair, and the ability to take a full tank of fuel without leaking!

Do you have a fuel leak then?

[pjw12]

there's a defiantly a fuely smell, and the first 1/4 of a tank of fuel goes down pretty rapidly, so i strongly suspect there is. Want to get it sorted before 2000 mile trip to Europe at the end of July.

[Gordon]

there's a defiantly a fuely smell, and the first 1/4 of a tank of fuel goes down pretty rapidly.

Exactly the same symptoms as mine

Best of luck.

[pjw12]

Hmm, doesnt look too difficult to do ( but then I do have a 12 bay main dealer workshop..)

did you remove the lower strap fixings via the N/S speaker pod or just undo the upper ones?

[Gordon]

Hmm, doesnt look too difficult to do ( but then I do have a 12 bay main dealer workshop..)

did you remove the lower strap fixings via the N/S speaker pod or just undo the upper ones?

The manual only suggests removing the top ones.
As the car has to be high enough in the air to swing the wishbone down, the straps also just swing out of the way - removing them would be of no help.

[pjw12]

ah, didnt realise they were hinged! took a total of 5 hours to do, the neck had a crack running around the seal between tank and insert, unlike the radial cracks that have been posted on here

[lotuselanman]

There was a recall for the petrol tank, which the Lotus dealership has ordered for me. They will replace it next week hopefully at no charge. The recall was issued in 2002 I think... I have a horrible stench of petrol so hope this will fix the problem

[Brit-Car-Nut]

FYI, the recall is just for US/Federal cars.

[tigerdog]

FYI, the recall is just for US/Federal cars.

Correct.