The Definitive Fuel Tank Guide - LotusTalk - The Lotus Cars Community
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post #1 of 132 (permalink) Old 10-11-2013, 02:51 PM Thread Starter
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The Definitive Fuel Tank Guide

I know the title sounds grandiose, but the fact is that we have pulled and repaired or replaced tanks in SEVEN Esprits years 89-95! We have a set of V8 tanks(vintage unknown) that have the same problem and construction.

EVERY car we have dealt with including the latest which is Artie B's car, have severe tank corrosion. Three cars were seeping fuel wihout us or the previous owner being aware till we pulled the tank.

The tanks all show the same pattern of rust. All the perforations and severe corrosion is happening on the bottom under the foam, at the rear portion near or at the lip.

All the severe corrosion is UNDER the foam. More modest non severe corrosion occurs on top. Only minor superficial rust occurs on the tank sides or the sump where there is no foam.

In our sample drivers side tanks seem to go first most of the time, but corrosion on the passenger side can also be significant.

The pictures show examples of corroded tanks.
Picture 1 is a pair with one leaking.

Picture 2 shows the foam pads. The two rust colored pads are the bottom pads from Artie B's car. The rust color IS rust, sheets of rust! The cleaner pad is the upper.

Picture 3 shows a leaking tank from my 89 SE before we cut it out. Note the top looks fine.

Picture 4 shows a ground and in process repair, but note the extensive pitting.

Picture 5 shows a repaired tank using the POR product for exterior and interior coating.

We have also had aluminum tanks built as replacements.

So if you have your motor out pull your tanks, inspect the bottoms and pull the foam. You ca get under the car and take a look, but unfortunately the problem area is not accessible.

I strongly advise against using foam on the reinstall. Instead we use 2" squares of rubber to set the tank on and on top to provide compression for the tank hold down plywood.

For those that have thought of, or suggested doing something with the tanks like pouring something "down in there", you are wasting your time! Do it right or don't waste your time.

Randy
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post #2 of 132 (permalink) Old 10-11-2013, 04:18 PM
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Thanks for that.
You have reassured me on this problem.
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post #3 of 132 (permalink) Old 10-11-2013, 04:46 PM
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How much are aluminum tanks?

Can we have them made with AN fittings?

1998 Esprit V8.
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post #4 of 132 (permalink) Old 10-11-2013, 05:08 PM
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Aluminum might not be a better choice...

The steel tanks rust because their paint coating is scraped off as they are installed in the rough fiberglass wells. The bottom edge is also constantly rubbing on the fiberglass.

I put rubber u-channel on the edges of my fuel tank seams, and a rubber mat under each tank. The u-channels are sealed with silicone sealant so water can't get trapped in there. I replaced the foam with a closed cell foam and glued thick plastic sheeting to both sides. The tanks are still grounded through their grounding straps.




The tanks were totally stripped, rust cleaned off. Then I used the POR-15 system of the metal ready phosphoric acid, and then cleaner to clean out the insides of the tanks. Coated the insides with POR-15 epoxy. And then coated the outsides with a rust inhibiting primer and many layers of a truck bed liner paint.

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post #5 of 132 (permalink) Old 10-11-2013, 05:21 PM Thread Starter
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Originally Posted by FSReric View Post
How much are aluminum tanks?

Can we have them made with AN fittings?
Alu tanks will run $350-400 per tank. AN fittings should be no problem, but we had ours made to fit the original fuel pump module.
They are a bit lighter, and more corrosion resistant as long as you don't foam them.

We had 3 pair built. Another local Esprit owner just had a pair built by the same company, and he did some more design work on them. They should be showing up anyday now and I will get some pics of them and post them. I believe he is going with AN fittings.

The first 3 pics are of aluminum tanks installed in our S4.

The last 2 pics are of the V8 tanks that we have. Same foam, same paint same steel, meaning tin can construction. As you can see the paint is peeling and rusty.
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post #6 of 132 (permalink) Old 10-11-2013, 05:38 PM
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Originally Posted by 89.5 Esprit SE View Post
In our sample drivers side tanks seem to go first most of the time….... but corrosion on the passenger side can also be significant.
Drivers' arse sweating to much

and a little bit of the passenders'

Thank for the good write up. More good to know info for prospective owner. The Espit definitely intrigues me but very hesitant on the cost of ownership..

When i do get tired (if i get tired of my Elise) i might just jump in for a well documented one.

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post #7 of 132 (permalink) Old 10-11-2013, 05:55 PM Thread Starter
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Aluminum might not be a better choice...

The steel tanks rust because their paint coating is scraped off as they are installed in the rough fiberglass wells. The bottom edge is also constantly rubbing on the fiberglass.

The tanks were totally stripped, rust cleaned off. Then I used the POR-15 system of the metal ready phosphoric acid, and then cleaner to clean out the insides of the tanks. Coated the insides with POR-15 epoxy. And then coated the outsides with a rust inhibiting primer and many layers of a truck bed liner paint.
Travis, I think what you did should work well, and the closed cell foam is a much better idea.

However, Lotus used a rubber channel on the edges on later cars including the V8, which prevents the edge from rubbing the fiberglass. they did not seal it to keep water out.
While we do see the lower edges corroding significantly, all the perforations we have were on the tank body adjacent to the lip wherre the foam traps the moisture between the tank and the fiberglass shelf. You can see this well by looking at the foam pads above.

We built our aluminum tanks without the lip, and instead set the tanks on non-porous rubber pads which will not trap moisture. The tank is held in place with pressure from above, the bolt which is also used for grounding, and a couple rubber shims at the lower corners, not to mention the filler pipe.

I think the choice between refurbishing and a new aluminum tank is close to a tossup.

The DIY refurbishing with POR 15 works well, but is a lot of work. It will run about $100 for both tanks. We have done this now with several pairs of tanks. If you don't do it right it will not give a good result, and we have a tank in the shop done by a PO that was done poorly with an incomplete coating of the interior.

You can have the tanks proffesionally restored for about $300 or so according to Jeff at JAE, and the work is supposed to be high quality.

The aluminum will run a tiny bit more, but will be lighter and last longer if properly installed.

Randy
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post #8 of 132 (permalink) Old 10-11-2013, 06:13 PM
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My tanks were most rusty on the raised lip seams. Then just as you said, the foam had held moisture against the tanks and they rusted there too.

Even though my car is a dry climate car with zero rust anywhere else, my tanks were rusty, inside and out. No holes, just surface rust.

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post #9 of 132 (permalink) Old 10-11-2013, 06:55 PM
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Nice write-up Randy

Ditto on everything you said and particularly about trying to coat the tanks in the car. With the baffles in the tanks there's no way you could do a proper preparation of the surfaces and get coverage
of the sealer and then get all the excess out. I can only imagine the problems that could cause...

Jim
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post #10 of 132 (permalink) Old 10-11-2013, 08:12 PM
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Does Boyds make your aluminum tanks? You should ask them about having the tanks anodized. That would allow you to run high ethanol content fuel without having the ethanol corrode the aluminum. An example would be if someone converted their Esprit to run on E85. It's a small price to add to the tanks and gives the aluminum a more durable finish, inside and out.
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post #11 of 132 (permalink) Old 10-11-2013, 08:42 PM
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Randy, thank you for this excellent "technical bulletin".

Unfortunately, under-the-foam corrosion is not the only problem.
Rusting from inside out plagues all British made vintage cars.
Ethanol is the culprit.

Users of ethanol/gasoline mix found an unsuspected cause of trouble in the gasoline tank, which traditionally has been made of "terne plate," a favorite roofing material of Victorian architects. It is steel sheet coated with 8% tin-lead, making it ideal for resisting rust from water in gas tanks. Methanol reacts with lead, slowly but surely, forming a flaky sludge that plugs filters in the fuel system. The easiest solution is to inspect and clean the filters every few months while using methanol fuel.

On pre-1989 Esprits fuel tanks rust from the inside-out and primary pump ingests rust flakes rendering it incapable of supplying enough fuel to support secondary pump demand. This, in turn, causes low System Pressure and fuel starvation at higher rpm.

On Bosch CIS cars there is only one fuel filter situated AFTER the pumps and the accumulator. Unfortunately, there is no strainer/filter between fuel tank and primary pump intake leaving pumps unprotected.

Once the protective Terne-Plate coating is compromised your tanks will deteriorate pretty fast. Use of any kind of accelerators speeds up the rusting process. Sooner or later they will require epoxy coating or total replacement.



Picture 1. shows the initial phase of the Terne-plate destruction.
Picture 2. After flaking stops, unprotected steel produces large amounts of very fine rust particles clogging filters and jamming pumps.
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post #12 of 132 (permalink) Old 10-12-2013, 03:26 AM Thread Starter
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Quote:
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Does Boyds make your aluminum tanks? You should ask them about having the tanks anodized. That would allow you to run high ethanol content fuel without having the ethanol corrode the aluminum. An example would be if someone converted their Esprit to run on E85. It's a small price to add to the tanks and gives the aluminum a more durable finish, inside and out.
Quote:
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Does Boyds make your aluminum tanks? You should ask them about having the tanks anodized. That would allow you to run high ethanol content fuel without having the ethanol corrode the aluminum. An example would be if someone converted their Esprit to run on E85. It's a small price to add to the tanks and gives the aluminum a more durable finish, inside and out.
Yes Boyd's is the builder we used. They are in Ocala Fl and specialize in car and boat fuel tanks.

The issue with ethanol is both it's corrosive effects, and it's tendency to absorb water. Then when it sits too long it can "phase separate" meaning the water and alcohol separate from the gasoline creating a very corrosive layer which won't burn well and clogs up the fuel system.

For cars that are not driven often (weekly) and especially cars layed up for the season this is a big problem.

I will certainly ask their opinion about that issue. More relevant may be the soon to be released E15 which is more corrosive that the current E10.
Being that the car was not designed for E15, let alone E85 I would avoid them.

Randy
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post #13 of 132 (permalink) Old 10-12-2013, 03:39 AM Thread Starter
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[QUOTE=MRDANGERUS;2540138]Randy, thank you for this excellent "technical bulletin".

Unfortunately, under-the-foam corrosion is not the only problem.
Rusting from inside out plagues all British made vintage cars.
Methanol is the culprit.

MRDANGERUS that is quite interesting. Other than racing fuels are any pump fuels currently being sold with methanol?

We don't see much corrosion or sediment inside our tanks, even with extensive external corrosion. Also the fuel pickup is screened on the Stevens cars.

Was there a change in the type of steel used?
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post #14 of 132 (permalink) Old 10-12-2013, 06:18 AM
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Great write-up and pics, Randy.

Just to consolidate some of the measures from gas-tank topics elsewhere, here are things an owner can do to preserve existing tanks.


1. Prevent water egress* [ *A path or opening for going out; an exit.] above the tanks.


This means, repair any peeling or crinkling on the black edges of the quarter windows (harder to see on G-bodies). Once removed and re-primered, put an extra bead of sensor safe RTV around the window on the back-side. Lotus used a thin bead, there is plenty of room for more and it will not show.

Also, RTV around the junctions of the air ducting on both sides. These are riveted on the inside. They are not especially water-tight.




2. Prevent water egress through the wheel wells

There are two through-bolts on the forward side of both wheel housings. The bolts support the upper tank-boards. Clean any undercoating from the bolt-heads, seal with RTV on the wheel side, then re-undercoat the wheel wells.




3. Prevent water egress into the underside area of the tanks.

Four-cylinder owners can install rubber seals on the engine bay undertray (or, on the bodywork around the large tank access holes). I used a bulb seal 1/8" high from the Home Depot.


+++++++++++++

I pulled my OE tanks for inspection during my engine refresh, and found that these measures had prevented most of the corrosion. In fact, my OE tanks were still sound, so I just had to POR-15 the surface rust on the outside and reinstall them.

My car had been driven for long periods through many wet conditions (Hurricane George in '98 and Hurricane Katrina in '05). In both those years, we drove in downpours for 6 - 8 hours straight...


I also used silicone hose beading to protect the upper and lower flanges instead of any foam on the underside when I put my tanks back in.


Further, be careful when washing your Esprit. Don't use a high-pressure spray around the rear quarter windows or air vents (both near the windows and in the lower sill).


One final thing I do is run a dehumidifier in my Lotus's garage. This is especially important where daily drivers share the space.

Atwell Haines
'88 Esprit
Succasunna, NJ USA


"Not all angels have wings." - Turbo R

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post #15 of 132 (permalink) Old 10-12-2013, 07:10 AM
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Water around the fuel fillers is probably#1!

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post #16 of 132 (permalink) Old 10-12-2013, 11:32 AM Thread Starter
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Totally agree with Atwell and Travis on the water ingress issue.

Atwell those are all excellent suggestions. Many older Esprits have leaky quarter windows, and even those of us who rarely drive in the rain will get leaks just from washing the car.

On the positive side, when the tanks are redone with POR15 and without foam underneath they tolerate the water a lot better.

Randy
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post #17 of 132 (permalink) Old 10-12-2013, 12:59 PM
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Originally Posted by Vulcan Grey View Post
Water around the fuel fillers is probably#1!
I forgot to mention that possibility, but Bosch FI cars are different than GM FI cars in the filler and cap areas.



My Bosch FI fillers (the ones that cross to the "eared" Scirocco fuel caps) have a rubber gasket on each side of the filler-to-body contact area. On my car, the rubber was doing it's job, as it is almost totally covered by the metal flange on the outside.

There was NO evidence of any water getting past them when I removed my fillers last year. That includes around the neck itself, and through the filler door releases, which are cable-operated on the '88s but electrically released on '89-up cars.




I understand that the screw-in GM style click-caps had a different filler-neck gasket that could, and would, deteriorate. That's worth a look, for sure.




It's worth noting that many G-bodied cars had rusty tanks, and those bodies had exposed fuel caps, so the fuel filler-neck sealing deserves a close look.

Atwell Haines
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post #18 of 132 (permalink) Old 10-17-2013, 04:12 PM
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Here's an interesting suggestion: would it be possible to perhaps organize a "Group Buy" of the aluminum tanks from Boyd's?

If not, can individuals can order aluminum tanks for the G-Esprit (mine's an '86) from Boyd's? Their website shows a pair of tanks at US $750 for the Esprit, but I'm honestly not sure if it's a "one size fits all" application, or if they have templates for both Steven's Esprits and G-Esprits on hand (the posts seemed to indicate the tanks were mostly "one off" designs fitted solely to the Steven's design cars).


By the way, excellent suggestions regarding keeping moisture out of the gas tanks. Interestingly, the owner's manual for my '86 (it's actually the manual for an '85, oddly) specifically notes that using "Gasohol" (10% ethanol blend) is okay to use, but non-ethanol 95 (!) octane gas is preferred. Guess no one at the time knew what the long-term effects of ethanol would be (my tank is rusting from the inside out, from what I've been told).

Cheers,

Scott

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post #19 of 132 (permalink) Old 10-17-2013, 05:33 PM Thread Starter
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Here's an interesting suggestion: would it be possible to perhaps organize a "Group Buy" of the aluminum tanks from Boyd's?

If not, can individuals can order aluminum tanks for the G-Esprit (mine's an '86) from Boyd's? Their website shows a pair of tanks at US $750 for the Esprit, but I'm honestly not sure if it's a "one size fits all" application, or if they have templates for both Steven's Esprits and G-Esprits on hand (the posts seemed to indicate the tanks were mostly "one off" designs fitted solely to the Steven's design cars).


Cheers,

Scott
I have no idea whether the G car tank is the same size and shape. I'm sure there is some variability in fittings and placement of the sender and fuel pump.

One of our shop partners just had Boyd do a pair for his SE, they look very nice.

I can't speak for Boyd except to say they do good work. The first time we bought 3 pair of tanks and received a modest discount.

Even so $750 for a pair of tanks is a good price. A group buy would only save a little and would be a big undertaking.

Randy
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post #20 of 132 (permalink) Old 10-17-2013, 07:29 PM
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Well, it's worth a look, then!

And I agree fully: compared to the price of importing alloy tanks from the UK [at a 1.6 approx USD to GBP exchange rate] of US $832 plus international shipping, ordering them from Boyd's is a logical, intelligent financial decision for any G-Esprit owner, regardless of the shape of the fuel tanks.

Cheers,

Scott
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