Classic cars forum & vehicle restoration.

[Aircool]

Hi, We recently bought a 1937 Morris 12/4 Series 3 (have not owned a classic before) and at the petrol station I filled it up until the fuel was visible at the filler cap, to my dismay I noticed that petrol was pouring out from the tank, I couldn't identify where.

However with the car came with a host of spares including a very serviceable fuel tank so yesterday I stripped the paint from the tank wire brushed it ready for some paint, I noticed that on the top of the tank is a soldered flange with a 3/8" hole in the centre, upon further investigation I realised that this is a vent for the tank (with a baffle inside) and realised that if the tank is filled to the brim of the filler pipe then petrol would indeed come out of this vent, this is probably what was happening to the original tank at the station

Therefore my question is should there be a valve or something in the vent hole or does the tank permanently vent to atmosphere?

Finally does anyone else here have a series 3, I have been told that these are quite rare which may not be a good thing when it comes to spares, do they share parts with other cars?

[roverdriver]

I'm not familiar with your particular model, however a couple of general observations.

The tank needs to vent to the atmosphere somehow.

Usually this is done with a vent pipe. Sometimes the pipe extends well above the tank.

It would not be usual for there to be a valve as the flow of air goes both ways- out when filling the tank and out as fuel expands in warm conditions, and in as the fuel is used or contracts.

In your situation, I would suggest fitting an extension on the vent pipe so that the end of the vent is above the neck-height of the filler pipe. You would need to work out a suitable route for that vent pipe so that no noxious vapours can get into dangerous places!

Until someone with particular knowledge of your model comes along, I hope that is of some help.
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Dane- roverdriver but not a Viking.

[Phil - Nottingham]

On my 1939 Rover 16 P2 the vent pipe from the top of the tank has a rubber tube to extend it to just below the neck of the filler pipe under the cap - this means no escaping fumes or fuel - this is a usual arrangement for low rear mounted tanks although on the P5's of the 1960's the vent pipes are very complicated and buase tank is behind rear seat the end of the pipe finally finishes underneath the car (where it can block).

I suggest you do have a missing pipe - look for a spigot to fit the end into the filler pipe neck
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[Aircool]

Hi, Thanks for that, it seems feasible, however I cannot find where the other end of the pipe would re-enter the filler, also I can't really see the point beacuse if it was located fuel side of the cap then the it couldn't vent (both ends being at the same pressure). Possibly a Tee could be involved one to the filler tube and one to atmosphere at a higher level than the cap?

[Rick]

Are you able to post a photo of the spare tank, with the 3/8" hole you mentioned?

R
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[Aircool]

Here it is:-



The plate you can just see through the hole I think is a baffle, there appears to be little or no restriction when I blow through it.

Steve

[buzzy bee]

Hi

I would attatch a piece of tube, which will stand petrol, up from the vent, following the filler neck and stop just short of where it comes out, so it is still venting to atmosphere and it is not venting fumes anywhere there aren't allready present.

Cheers

Dave

[Aircool]

Hi Dave,

Yes I think a grommet with a lenght of rubber tube welded to it would do the job, I am interested in exactly how it was designed though...

Steve

[Nic Jarman]

If you have a look at the second picture down you can see on my Morris 8 tank the same breather. I filled the car with the nozzle pushed well into the tank and this did not cause any leakage. Sounds like you overfilled the tank but check the rubber tube is not split.
http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=6835
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

[Aircool]

Hi Nic,

Are you saying that there is a rubber tube in your breather or are you referring to the rubber filling tube between the metal filling tube and the tank when you say it could be split? If so I have checked this one.

If there is a rubber tube in your breather, where did the other end of your tube locate?

If not I'm not sure if there is a tube in my existing tank, by the rate petrol was pouring onto the forecourt I strongly suspect not, other possibility is that the seal around the sender has rotted, or the soldered seal along the width of the tank has opened.

Although after saying that there is no smell of fuel around the car, so it can't be major...

When it stops raining I'll finish spraying the spare tank and take the old tank out. then all will be revealed.

Steve

[Nic Jarman]

Steve I did mean the filler tube. If the tank is not compromised then it is just overfilling. Welcome to 1930s motoring. Re-soldering a tank is pretty easy and I made a new sender seal with cork sheet gasket. OK I must go now and fill my tank - carefully.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

[Aircool]

Cheers Nic, I think perhaps that I've been overfed on technology through the years, did they really fill the tank untill it came out the vent But I suppose at a tanner a gallon it didn't matter that much and health & safety hadn't been thought of . I'll be interested to get the old tank out.