The Lotus Cars Community banner

1 - 20 of 38 Posts

·
Registered
Joined
·
184 Posts
Discussion Starter #1
Just curious...what's it for? Although it's slightly thicker than the metal lip of the tank, I think it's too soft to provide enough support to keep the lip from contacting the body. Am I mistaken? Does it prevent body contact after all? Does it serve some other purpose like noise suppression? Or is it possible it's just there to retain moisture? :D
 

·
Registered
Joined
·
3,384 Posts
It's original purpose was sound absorption. Due to the Law of Unintended Consequences it's other purpose is to retain moisture and rot the tank. Or you might consider it a built-in obsolescence feature that contributes to your mechanic's children's college fund.
David Teitelbaum
 

·
Registered
Joined
·
184 Posts
Discussion Starter #3
Thanks...that's pretty much how it seemed, but I thought I might be missing something.


It's original purpose was sound absorption. Due to the Law of Unintended Consequences it's other purpose is to retain moisture and rot the tank. Or you might consider it a built-in obsolescence feature that contributes to your mechanic's children's college fund.
David Teitelbaum
 

·
Registered
Joined
·
576 Posts
The purpose of the foam is actually unknown. There is no sloshing sound when it is gone, and it only covers 2 sides of the tank. Is it there to minimize temperature fluctuations? Same answer. Does it keep the tanks from developing an obnoxious resonance? I haven't noted it in any of the now 4 cars we have without it.

Maybe someone at Lotus had a brother in the carpet business!

The only thing that I have seen the foam do well is cause rust and sponge up the gas leaking out of the pinholes.

Get rid of it ASAP

Randy
 

·
Registered
Joined
·
1,231 Posts
The purpose is to rot out the tanks with moisture retention so you will have to replace them. The tanks alone cost a small fortune and realistically you will have to pull the engine or go through some incredible misery trying to get the old tanks out and the new tanks in when yours starting leaking fuel.

I love the Esprit to a point approaching insanity, but the fuel tank design was a horrible mistake.
 

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
5,861 Posts
Just curious...what's it for? Although it's slightly thicker than the metal lip of the tank, I think it's too soft to provide enough support to keep the lip from contacting the body.
I was going to glue some inch-long, slit pieces of vacuum hose (only the finest silicone hose, of course :bow: ) to the top & bottom flanges before I reinstall my OE tanks. That way the lip of the tanks will not touch anything...

Hopefully, any movement from road vibrations (or those bumpy FIA curbs at the racetrack rotfl ) will occur between the hose and the fiberglass body, NOT the tank metal.
 

·
Registered
Joined
·
1,231 Posts
That's a good idea. When we put in the aluminum tanks (no lip on the tank) we set them on 4 hard rubber feet which RTV to the floor of the car. That way you get some air space under the tank.
 

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
5,861 Posts
< opens wallet to unfold pictures >

Here's MY picture. This is the bottom of the left tank. (Same surface as the upper tank in Tom's picture.) Right side tank had no rust (and was the most difficult to remove, of course) :rolleyes:

It was all surface rust, so, both tanks were coated in POR-15, and are ready to reinstall.

Dale, I think Lotus intended that the small square pad of leftover carpet jute at the outboard, front corner would isolate the tanks from chafing. :huh: It was nice that they didn't waste material after finishing the interiors...
 

Attachments

·
Registered
Joined
·
576 Posts
I have seen Lotus use a rubber gasket like material on the tank lips in the chafe areas, but it seemed to just aggregate rust issues as it trapped moisture.

The slit hose in short pieces is a better idea as it will not retain moisture as readily.

BTW on steel tanks moisture is the killer. On aluminum tanks moisture is only a problem when there is no Oxygen(air) circulation. That is because in the presence of air aluminum corrosion is protective to the surface below. That is not true of steel. On boat installation aluminum tanks have only been a problem when they are foamed in place and water enters between the tank and the foam leading to pinholes.

Randy
 

·
Registered
Joined
·
576 Posts
Moisture gets to the tank in three ways.
Water in the fuel, condensation on the INSIDE of the tanks coming through the vents, and condensation on the outside. These happen to everyone.

The other not so rare way especially on older cars is water entering through leaky quarter windows.

So not driving in the rain and being very careful when washing your car will minimize moisture issues.

However water in the fuel can happen to anyone, and condensation is a problem for anyone not living in the dessert.

Don't believe you will get much benefit from a moisture absorbing substance unless you have a tiny hermetically sealed garage to park your car in.

Randy
 

·
Registered
Joined
·
3,384 Posts
It should be obvious Lotus was not very concerned about the car lasting for a long time without extensive maintenance. Since their basic philosophy is to build a light race car, and race cars were not expected to last, it makes sense they did not build with materials that would last a long time or add weight. As a further tribute to frugality it also makes sense they would use what they had left over from other areas of the car. Not only did they not have to buy materiel for this, it also saved them money on trash removal! Less stuff going into the garbage!
David Teitelbaum
 

·
Banned
Joined
·
1,594 Posts
They were suppose to have changed the coating for the fuel tanks around 1998 to improve the situation but it's not clear that helped.
 

·
Wingless Wonder
1988 Esprit Turbo
Joined
·
5,861 Posts
It should be obvious Lotus was not very concerned about the car lasting for a long time without extensive maintenance.
David Teitelbaum
Well, FWIW, most cars back in the 70s (when the Esprit was first designed) came with steel tanks. Depending on the car, these tanks would sometimes only last 5 years before they rusted externally. (Why oh Why do I always end up with these????) :shrug:

Later on, the plastic fuel tank came into vogue. They had their own problems, as did plastic radiator tanks. (Ask any M100 or Dodge Van owner)

So let's not say that Lotus was "unconcerned", they just used whatever was typical for the time (like Lucas or Bosch electrics)
 

·
Registered
Joined
·
1,293 Posts
One other way that water gets to the tanks is through the hole in the body where the fuel filler flap hinge passes through. Personally I think this accounts for a lot of the water damage seen. I have pics showing water stains from the hole to the top of the tank and large rust spots on the tank right where it drips.

I'm not sure whether it was intended or not but one function of the foam is to provide some holding pressure on the tanks to limit movement when the plywood decks are bolted on top. The only other mounting point for each tank is a single bolt at the bottom.

On the tanks I've refurbished, I usually use some closed cell rubber foam pieces on top and bottom for the extra cushion even if it doesn't cover the entire top or bottom of the tank.

I've pulled rusted tanks on 5 different Esprits now and none had leaking 1/4 windows...
 

·
Banned
Joined
·
1,594 Posts
That's good info, Jim! I will find a way to stop the water coming through that hinge.

When I got my car, I found it had a small leak on the driver's side quarter window when I washed it.

My car is a fair weather car with me, and the PO kept it out of the rain (confirmed his claims by the complete lack of corrosion and the ease to get off any bolt so far), but I want it to be water proof.

I was able to put specific windscreen silicon sealer (that stuff sticks like a motha) between the 1/8" gap of the fiberglass and the window. It's a contortionist thing to do, but still much better to me than risking breaking the glass to take it out. It's easy to test if you got it sealed with a water spray. Both of my windows are water tight now.
 

·
Registered
Joined
·
184 Posts
Discussion Starter #18
Dale, I think Lotus intended that the small square pad of leftover carpet jute at the outboard, front corner would isolate the tanks from chafing. :huh: It was nice that they didn't waste material after finishing the interiors...
I think putting the hose on the lip is a great idea. If it had come from the factory that way, I don't think the tanks would have had any problems.

As for the non-waste you mention, one of my favorite Lotus anecdotes is that when an engineer was once asked if it was frustration trying to build great cars while always having to cut corners, his reply was something to the affect of, "Not at all. Here at Lotus we are cheap and cheerful!"

I guess they didn't have any left-over hose bits lying around, though, so we got rusty tanks :)
 

·
Banned
Joined
·
1,594 Posts
One other way that water gets to the tanks is through the hole in the body where the fuel filler flap hinge passes through. Personally I think this accounts for a lot of the water damage seen. I have pics showing water stains from the hole to the top of the tank and large rust spots on the tank right where it drips.
I just checked this on my car and I can't see how the water can get in to the tank area through the gas cap flap hinge.

The hinge goes into the air intake area which doesn't go into the tank area.

What am I missing?
 

Attachments

1 - 20 of 38 Posts
Top