Brett928S2

Hi All

The fuel breather tank ...the long black plastic one that is fitted in the rear wing above the wheel....

Does it actually do anything ?

The reason I ask is that my car went through its annual MOT check today in the UK... (a mechanical and body check on all safety and general items)

That tank had dropped and was rubbing on the rear tyre and after removing it , it had obviously been doing it for a while as its was split from the rubbing...

The metal pipe that runs round the back from it to the rear PU had rotted away years ago and I never bothered replacing it..

Its called an "Expansion Tank" in Pet 7 but I cannot really see the point in replacing it as the weather in the UK is rarely hot enough to allow fuel to expand if thats its purpose >>> ???

Any advice appreciated...after removing it , I filled my tank to the brim (£94 worth ) and there is no leaking or fuel smell at all...

I am inclined not to bother replacing it unless anyone knows better...

So is it worth replacing for new, plus all the metal breather piping at the rear or no point ???

All the best Brett

ubercooper

Im using the stock tank and don't have one so Im guessing you'll be alright. However I dont have a stock motor or fuel system so I cant say for sure if its completely safe for you.

Brett928S2

Hi All

Number 14 in the Pet illustration is the part I am taking about and its big....around 20 inches long roughly....

Someone suggested it may be a part that some countries didnt have due to it being needed for emissions etc ???

All the best Brett

James Bailey

Part of the fuel vapor recovery system designed to hold any liquid fuel that might expand up out of the tank if you had it completely full with cold fuel from the underground tank and parked it in the sun in a 100 degree day...... Oh right never mind

Leon Speed

It might also store fuel vapours I am guessing.

Dave928S

It wiil have a worthwhile effect when you have the car parked on a cross slope with the fuel tank filler down. In that situation, if the tank was full, you could have an air pocket trapped on the left side which would expand with temperature and push fuel out into the expansion tank, instead of onto the ground.

You can get rid of the expansion tank as long as you avoid filling the fuel tank brim full, to leave a bit of room for expansion, and also avoid parking with the tank filler down on a cross slope. The charcoal canister up front takes care of vapour storage. Very old (standard Fords, GM, etc) cars don't have either.

James Bailey

Note that item 19 if the one way check valve...allows the tank to inhale but never exhale. The charcoal canister in the right front wheel well is plumbed to capture all the fumes. Then when the engine is warm and running it pulls some air from the can to purge those vapors.

Tony

having just got back from a week in England...it may not have been 100 but it may as well have been ! Unreal weather over there right now...in Devon atleast.

PorKen

19 is the 'tip-over' valve mounted vertically in the right rear fender. Inside the valve, a large ballbearing closes the breather line if the car is upside down.

The fuel tank normally inhales and exhales through the breather line, replacing burned fuel, and allowing vapors to escape.

lukipuki

19 is not a one way check valve!it works like Ken said.

James Bailey

Then where is the one way check valve because the tank is supposed to be sealed California is now pressurising the tanks to check the vapor recovery systems.....

Dave928S

There isn't a check valve that I'm aware of, just the inversion valve. Even if there was on that section of vent pipe, the expansion tank wouldn't function, because air wouldn't have a way out to let the fuel in from the neck tee piece.

I wondered after your post whether the inversion valve might also function as a check valve, to a minimum pressure, to encourage vapour flow to the front charcoal canister, but I've just pressure tested my 82, and it definitely is free flowing to atmosphere.

Interestingly on mine the vent line from the rear goes all the way forward in the top of the wheel well, down at the front and up into the bracket mounted inversion valve behind the front splash shield, then up and towards the rear into the expansion tank, with a line from the rear of the tank to the filler neck. This longer arrangement is factory but not as shown in PET.

Looks like anyone in sunny California is SOL if they have a 928 and it gets tested ... if US cars are the same as ROW in this respect.

PorKen

They would have to pinch the outlet hose (A) closed if they test for a completely sealed system.

James Bailey

O K so how does the tank collapse when the vent fails to inhale.....and it has happened to several 928 s. It is a sealed system and never exhales. One reason why they pressure test the gas caps as well (but not on the 928 because they lack the correct adapter) to make sure no vapors escape. And yes the vapor recovery ties into the plumbing for the overflow tank.

lukipuki

On row cars it is not a sealed system!,it allways inhales en exhales.
It is a very simple line with only the inversion valve for safety.


the vapor recovery system with the charcoil canister was only for UScars,for ROW this was
optioncode MO26.