another unknown reservoir
 

Under the left fender on my '85 Carrera there is a reservoir located over the main one and linked to it by the same bolt witch fasten both to the body.
The shape of this little plastic tank remind that of the intensive washer's one but it is not under the boot but, I repeat, under the left fender and again there is no switch on the right side under the instruments.
Does anyone knows what is it?
Thank you very much!!

Catch tank for for the gas tank.

+1

The small line on it deteriorates over the years and leaks fuel. Replace if needed.

The area under the left fender is very prone to rust and it's rust right through to the battery area. It is recommended to remove the evaporator/overflow tank and the washer tank to clean out all the mud and gunk and then repair if necessary with rust paint.

You'll be glad you did. :)

Thank you very much: now the whole thing is clear!

Agreed, I recently did a A/C delete and was amazed at how much road gunk came out with the lines. So while under the left fender I did just that pull the two tanks gas/washer fluid and sure enough more road gunk up in there also you will be glad you cleaned it out.