Hi, I’ve got a question that I can’t seem to find an answer to. I have and r series scania with twin tanks. The main tank is 350 litres and the auxiliary tank is 500 litres. The sticker says the 350 tank must be filled first which I always do. I’m in Scotland today and I need diesel. I have been told to just get 250 litres to last today and get me back to the yard tomorrow but how do I fill it. Do I split it between the 2 tanks, just add it to the first tank or what?
Thanks martyn
Just fill your 350l tank fella, then the other one if it all won’t fit
If its gravity fed you can put it in either as both tanks will just level themselves out, thats how mine works
Yep, just fill the one and it will find its own level as you drive.
There might be a tap under the tank if u fill the main 350 tank and turn off. its what I do till I fill both up then turn back on or if someone else drives truck
I’ve always assumed its down to the fact that those with the warning stickers have a bigger bore feed pipe between the two tanks and if you fill the big tank first the weight/volume of the fuel will gravity feed quite quickly into the smaller tank which could cause it to blow back through the filler hole as you’re in the process of filling the smaller one, don’t know if that’s correct like I said it’s what I assumed to be the reason.
I always just fill whichever tank the stack pipe is in then you can’t go wrong.
Reef:
I’ve always assumed its down to the fact that those with the warning stickers have a bigger bore feed pipe between the two tanks and if you fill the big tank first the weight/volume of the fuel will gravity feed quite quickly into the smaller tank which could cause it to blow back through the filler hole as you’re in the process of filling the smaller one, don’t know if that’s correct like I said it’s what I assumed to be the reason.
No that’s not right mate, on My Scania the running tank is about 250lt, and the other tank is about 150lt, the stickers tell you to fill the running tank 1st. I quite often only fill that one, and as has been stated they find there own level. 
Also, on a previous Scania, it had equal sized tanks, and I had on occasion filled the slave tank only, and they still just find their own level
I just fill the one nearest the pump, works for me 
wing-nut:
I just fill the one nearest the pump, works for me
Yep used to work for me, on the old motor, but that 150lt tank is hopeless, so I always try and get the big tank(250lt size is relative) next to the pump
Thanks for the replies everyone. I just filled the main tank and as said over the next few miles the fuel gauge dropped as it found its own level. I got worried when I was searching for the answer and read lots of posts about people filling the wrong tank first and ending up with airlocks
Coffeeholic:
Yep, just fill the one and it will find its own level as you drive.
Just dont swap Tank Tops
do I remember correctly the old MAN VW 7.5 tonner
had an electric switch to change tanks with.
Whilst were on the subject of tanks any old timers want
to elaborate on the use of belly tanks etc
Catwalk or ‘toptank’ tanks were the thing on a tractor unit in the eighties, A local engineering firm made them for our firm. About eight inches deep and went full width of the truck, fitted just in front of the fifth wheel and forward to just behind the cab. A filler cap on one side, and a flexi pipe connected to a welded flange on top of the standard tank on the truck with an inline tap.
The only problem i had was when getting off the ferry from Calais one day at an extremely low tide, the angle of the linkway was such that it caused the very front of the trailer to dig into the top tank which split and resulted in me dumping oodles of diesel onto the linkway, popular I was not!
IIRC Belly tanks were fitted between the chassis rails of the trailer.
SWEDISH BLUE:
IIRC Belly tanks were fitted between the chassis rails of the trailer.
Correct. Over here they were usually about 1,000 L.
If its going down the Nerdy tanks off our past route, try this. Renault used to use a twin feed system on the twin tanks fitted to models such as Turboliners and early Magnums, there was a single feed and return from the engine, which started/finished at a junction box, where a feed and return came from each tank, the tank with the most diesel fed, which effectively meant they would be drawing together, as the levels balanced all the time. One drawback would be if the breather pipe on the tank which gave the fuel reading for the dash got blocked, as the diesel wouldn’t draw against the vacuum caused, and you had the potential to drain the other tank without realising 
hitch:
do I remember correctly the old MAN VW 7.5 tonner
had an electric switch to change tanks with.
Whilst were on the subject of tanks any old timers want
to elaborate on the use of belly tanks etc
Sort of. The old MAN had two small plastic tanks, side by side on the chassis. It also had an electric switch in the cab, but it only switched between the fuel gauge sender in each tank. Both tanks fed fuel together, as I found out to my cost 
I had recently left the army and our Landrovers had two separate tanks and a switch over lever in the cab. The MAN I drove read different levels for each tank, so I switched over to the low tank. Some time later that tank was reading almost empty, so I switched over to the full tank. I was rather surprised to discover that tank was almost empty as well. Luckily I reached a petrol station I could use before it started coughing 
Merc tanks equal out does not matter u can fill650 or 350 on mine
hiya …i was working for a chap in the 70s who supplied a car with the job. i,d just had a new motor off him
he said if your running your motor you can have some diesel out of the truck don’t go silly but have some.
one night i’am just talking 10 gallon(for two weeks) when i get a tap on the shoulder, i look round there stood one massive copper(think quick john) what you up to mate he said (i had a atki with twin tanks) i said just a moment as i swapped cans. the bloody kids climb all over these waggons at night and have broken the pickup pipe(there was no pipe) and showed the copper a piece of wood hammered into where the stack pipe went.i said every other night i have to fill this tank from the other side just because kids mess about(all this time i’am pouring the fuel into the tank)when its leveling itself out i’am getting another can to pour into the slave tank. the copper said you’ll stink when you,ve finished i’ll leave you to it and drove off. phew that was close, it was ok with the boss but the vat was’nt payed on the fuel i was having…morral is on Atkinsons the fuel does level out which ever tank you fill first.
John