S3 Fuel Expansion Tank

[Bob.]

Glad it helps.
Is your car an original UK one? I know it is much modified but given that it still has an expansion tank, where does the tank vent to? On US cars the vent is via a rubber hose from the tank to a steel pipe exiting the front of the boot to a carbon cannister in the engine bay, but I would like to know where the boot exit point is, if different, for the vent on non emissions cars given that all S3s had the expansion tank.

Bob

This is the exit point for the emissions version.

[jagwit]

Fantastic pics, thanks Bob!

Now comes the big question:

Which connections on the tank goes to which connections on the expansion tank?

I am aware of three connections on the tank but I see 4 connections on the expansion tank. I presume one of them would go to the carbon cannister or otherwise atmosphere (external to the body)?

[Bob.]

Hi Philip,

"D" is the outlet Jaguar designated for the expansion tank vent. The diagram shows the early type of charcoal cannister.

Two restrictors, which should be about 2 inches in from the ends of hoses "A" and "B" at the main tank end, will often have been unknowingly thrown out when hoses have been renewed, as mine had been. If you still have these I would be interested to know what the bore of these restrictors is - I suspect it is 40thou.
Note that the second picture kindly posted by someone else, shows the expansion tank upside down.

Hope this helps.

[jagwit]

Fantastic info! Thank you Bob!! I'll go see if my car has those restrictors.

[Fspp369]

Well it came out with a little help of a large blunt screwdriver. Thanks Bob.
Haven’t found any restrictions in the pipes but have found two round welded plates at the same points on the top of the wheel arches? Anyone have any ideas?

[Bob.]

Glad you got the expansion tank out without damaging it Peter. Where did the vent pipe exit the body?

Would you mind posting a picture of the plastic plug fitted to the small drain hole to the right of the sump hole in the boot floor. I can't see it in your picture, I think it's hidden under some flakes of something. Many, like mine, are missing and it's not shown in situ in the Parts Manual. I think it is BD25375, originally with a hole right through although the current aftermarket versions have closed ends.



Re the circular features in the panels shown in your pictures, are you sure they are welded in rather than just pressed in as stiffening/antiresonance features?

Are they as shown here or something else?

[Fspp369]

Rob
I see nothing as described, two Phots taken let me know.
I was deservedly ashamed of dirty boot, but in my defence I’m still stripping!!
Peter

[Bob.]

Thanks Peter, your plastic plug has also gone missing like mine.

[lowact]

Mine was still there, just ...

[Bob.]

Thanks Colin - that's what I thought it was, an open ended tube with two wings. I have plenty of pictures of the tube part poking out of the bottom of cars, albeit of differing lengths, but only one fuzzy image of the winged top part inside. It looks the same as that originally used in the doors to accept the metal clips of the door cards.

If anyone can help, I would still like to bottom out the issue of where the expansion tank vent pipe on a non USA/Canada car exits the bodywork.

[jagwit]

If anyone can help, I would still like to bottom out the issue of where the expansion tank vent pipe on a non USA/Canada car exits the bodywork.

This is on my S3 RHD OTS:

tn2_20210406_183845.jpg (134.35 KiB) Viewed 4463 times

[Bob.]

So whereas on an an emissions car the hose transitions to the steel pipe going to the carbon cannister before going through the grommet at the back of the boot, as shown in post#21, on a non emissions car the hose is simply poked maybe an inch or so through a grommet with a bigger hole and vents into the area above the IRS. It did see the most likely way but it's good to see some evidence as it does not seem to be documented anywhere - thanks Philip.

[Fspp369]

Colin
Do you have a picture of where this thing fits?

Bob you’re correct on closer examination it does appear to be a pressing mark.Ta! I note you’re about to transplant a rear wing I’ve got to do the same after discovering a poor wheel arch repair...what method are you going to use to add? Butt or joggled joint to the old stuff?
P

[Bob.]

Peter,
Sorry not my car in the picture, just used it to illustrate the panel feature. Other forum members will be able to help you with bodywork repair techniques.
Bob

[lowact]

Do you have a picture of where this thing fits?

This is on my S3 RHD OTS:

http://forum.etypeuk.com/download/file.php?id=1430

... on a non emissions car the hose ... vents into the area above the IRS ...thanks Philip.

Surely this would make the car incredibly smelly? Phil, is this correct, your tank is openly ventilated by this hose?

Or are non emission fuel tanks sealed, i.e. remove the filler cap on a hot day, is there a purge of pressurised air?

[Fspp369]

Now I am confused...
The thing shown in the closeup is approx 20mm long and at least 15mm dia on the body. The hole in the sump floor is 5mm how do the two marry? Why is it the shape it is?
I plan to get rid of the expansion tank and just have one small breather coming out of the top of the fuel filler tube and then down through the rear floor at the same point as the water drain from the boot/trunk lip.
P

[jagwit]

Surely this would make the car incredibly smelly? Phil, is this correct, your tank is openly ventilated by this hose?

The pipe comes from the expansion tank, goes through the body to the IRS cave and terminates there with an open pipe. But this open pipe may not be how it came from factory - this car having been "restored". The idea is for fumes to come OUT of that pipe but moist/dirty air can just as easily go INTO that pipe if the pressure inside the tank drops by cooling down. I recon a very small inline fuel filter should thus terminate that pipe.

[jagwit]

I plan to get rid of the expansion tank and just have one small breather coming out of the top of the fuel filler tube and then down through the rear floor at the same point as the water drain from the boot/trunk lip.
P

Don't. If you fill the tank and then park the car leaning downhill to the left, even just a little, you might get fuel being pushed out your breather pipe. Ask me how I know (when I mounted two 50L fuel tanks to my LR Discovery in place of the rear jump seats.)

[jagwit]

Or are non emission fuel tanks sealed, i.e. remove the filler cap on a hot day, is there a purge of pressurised air?

I've never had this but now I understand why. There can not be pressure in the tank with this breather.

[Fspp369]

My plan is to put the small breather just below the filler cap above the inside flap in the fill, tube so essentially as small and high as possible.using small kunifer copper tube.