Eau de essence( Benzine)

2003 Cabrio. A constant wif of the finest unleaded when parked up. There is no evidence , no wet patches either on the vehicle or the ground , even if we look as soon as we stop. I've checked the filler area ..all good . Is there a common place these tanks rot on the cabriolet version?

The tanks rot on the hardtop- should be the same, right on the spout. Mud from the back wheel covers the rubber filler pipe, gets between the rubber pipe and the metal spout and rots holes on the top side. A full tank will give a leak, less than full a smell, and the tank wont pressurise. I fixed mine with a smear of that plastic filler designed for fuel tank repairs and it lasted years.

There is a breather pipe running to a charcoal filter under the bonnet, this has a one way valve somewhere so you can blow down the pipe into the tank, and it holds a low pressure. If the tank over pressures vapour comes along the pipe and is absorbed by the charcoal. When the engine is started the filter is purged through a valve on the manifold. Overfilling the tank sends liquid fuel to the filter, makes it smell, and causes rough running for a few seconds after start-up.

Do check all 3 pipes from the tank, they have a habit of rotting through just under the drivers feet where they kink upwards along the chassis. A pinhole will leak enough for a lot of smell.

What an excellent explanation Facade!

I've very occasionally had rough-rounning after initial start-up and an occasional fuel smell - but there seemed no real pattern to it.

But with your explanation in mind I will make a concious effort to determine if this is after I fill the tank as I do have a habit of filling it to the brim. It may be that the fuel coming out of the cold ground-tank may warm up in the car's tank, expand, and thus overfill.

When I open the fuel filler cap there is slight underprepared in the tank and I hear a little suction noise. So I would think, if you hear this noise, then the fuel cost tank system is tight and the smell comes from somewhere else.

Max Headroom wrote:
I've very occasionally had rough-rounning after initial start-up and an occasional fuel smell - but there seemed no real pattern to it.

But with your explanation in mind I will make a concious effort to determine if this is after I fill the tank as I do have a habit of filling it to the brim. It may be that the fuel coming out of the cold ground-tank may warm up in the car's tank, expand, and thus overfill.

The tank is made so there is an air space at the top, which is an expansion space for the fuel as it warms up. This works nicely if the car is level when you fill the tank

If you keep trying to fill the tank after the pump cuts off, and shake the car etc. you get fuel in this space, and when it expands it will get into the carbon EVAP filter. After start-up, a valve opens on the manifold to purge the filter of fumes by drawing air through it. If it is full of fuel, fuel comes out too, and the engine runs over-rich for a few seconds (if it is really full, liquid fuel comes out of the air pipe on the EVAP filter).

The valve in the tank is supposed to stop liquid fuel flowing from the tank to the EVAP filter, either it wears out, or more likely it is made to give in extremis, otherwise the tank would burst, or the filler pipe come off.

If you must squeeze every last drop of fuel that you can into the tank (I used to do this) you need to immediately drive the car a few miles to use up the "extra"


If you blow down the tube from the EVAP canister to the tank (with your mouth, not an air line), you can pressurise the tank, and get a "hiss" if you immediately open the cap. In normal use as fuel is used up air enters the tank via a valve in the cap, this is sprung so it takes a little negative pressure to open, and you often get a hiss- ( or should it be a ssih ) as air enters the tank if you open it right after a run.

facade wrote: you often get a hiss- ( or should it be a ssih ) .

That right there cracked me up lmao!