Fuel tank inspection

[TSD]

I've read the horror stories about rust perforation and engine out replacement.

I'm not expecting any problems as mine car lived in Phoenix for the past 18 years, but better to be safe.

How to inspect? And is it true that the tanks sit on water absorbant foam? If so, what to replace with and how?

[DanR]

I've read the horror stories about rust perforation and engine out replacement.

On the S4 there's a hole underneath through which you may be able to feel if the foam's wet or damp. The other models may be the same.

As for a foam replacement, I searched my hardware store for a plastic door mat, the type that has softish spikes for wiping your shoes. My theory being that when it gets wet, with the tanks supported by the spikey side, the water can't collect but will drain more easily and there's better ventilation to dry things.

As for getting them out you may be able to do it without removing the engine. Raise the rear lid to near vertical, securely so it doesn't fall on your head, remove the boot tray and the other trim bits, the plenum chamber and exhaust manifold. The tanks may just slip through the gaps. As I'm not sure, be prepared to take the engine out if this doesn't work.

Good luck,

Danny.

[Splashout]

Hi I have replaced both tanks on mine and you can do it with the ngine in situ! Yes the tanks do sit on foam and this could well be what is the problem. As for inspecting them it is going to be hard to inspect them fully but there are a number of ways you can see bits of them. For the drivers side you can remove the air box that will give you a good view through there to that one and also there are the holes that the pipes such as on passenger side to fuel pump that you can look through.

But the tell tale sign is the smell of fuel in the cabin if you are not getting that then you should be ok.

If You wanted to have a good look the i would suggest taking out the boot floor and engine surround which would give you a verry good view.

[WayneB]

They say the reason the tanks rust is because the sealer holding the engine bay windows in fails and allows water to reach the foam that sits on the tanks. So even just washing the car can trigger corrosion! My car is just driven in summer but tanks still rusty,so even having a car from a dry state is no guarrantee this wont happen.

[Guest Troy Halliday]

When I stripped my S3 down I noticed a few things.

Yes the rear window surround had failed, and yes someone had tried to bodge it with bathroom sealer.

The rear quarter lights also had a small leak.

Oh and a leak through the cabin ventalation (on the B post near the door) had rotten my firewall/bulkead to powder so erm I think I may also have had a leak there also.

My Near side tank (left hand tank) has got a few holes in the bottem but my Off Side (right side tank) seems OK. This is not a big issue for me as I will be cutting the bottem out of the tank anyway to add a Collecter Pot for my Throttle Boddied Injection upgrade. I figure I can get about 0.75 L Collecter Pot on the bottem of the tank and still get it in and out. I am still considering ringing a few companies that make plastic tanks for the kit car industry to make my new tanks.

Mind you it was easy for me to inspect my tanks as they were stripped out along with everything else

[USAndretti42]

But the tell tale sign is the smell of fuel in the cabin if you are not getting that then you should be ok.

Note that fuel smells in the cabin can be the "surgical" pipe that runs above the window to connect the two fuel tanks and often perishes letting fumes into the cabin. Don;t assume your fuel tank has a hole if you smell fuel in the car.

[DanR]

But the tell tale sign is the smell of fuel in the cabin if you are not getting that then you should be ok...

That is if replacing the surgical hose hasn't helped.

By then the rust, being such an insidious cancer, has got to the fuel, making what could have been a simple repair a major one.

I'd suggest if ever there's a chance to take the tanks out for inspection do it. Preventative maintenance. The metal is about .8mm thick so any rust could be extensive but not quite through. More than likely, most tanks out there are resting on damp foam. Descale the rust, paint and replace the foam with something like plastic doormats, cut to shape.

I'm not sure if the top foam causes as much rust. It didn't in my case. Maybe someone can comment which side of their tanks was more rusted.