The BMW saddles


Just In case you want to drain your own bmw 7 series, 5 series or 3 series, some words of advice;

BMW’s by nature are low slung, they are also rear wheel drive, and have dual exhausts in most cases, which presents the designers a problem,  of “where do we put a 80 to 100 litre fuel tank on a car where space is an issue”

They answerd this question with “saddle tanks” – these look like saddles literally and hang over the transmission tunnel and exhuasts, in the fuel draining business we have another word for this which is “pain in the a***” the trouble with saddle tanks is you cant drain them from the filler neck,, well you can but you can only retrive 70% of the contents of the tank, so…..

Instructions for draining BMW, 3, 5, 6 & 7 (mid nineties onwards)

Ensure the work area complies with ATEX regulations.

Lift back seat up, this just requires a jerk on the bottom bench

Remove bench from car, take care not to let it get mucky

you have now exposed the top of the saddles, there are 2 access panels, which are obscured by the deafening foam, the foam lifts off and you now have 4 bolts to undo, undo the bolts and lift up the hatches, the sender wire will still be going thru the hatch, be carefull not to damage these. also disconnect the return line which feeds into the top – (this is a return line and cannot be used to drain becuase it doesnt go all the way to the bottom – so dont get your hopes up)

Take a moment, and remind yourself that your are in the interior of a luxury car and you are about to handle some of the smelliest liquids known to man, petrol and diesel will stain and stink for years, so be carefull.

you are now looking at the big metal donuts which hold the top of the tank and sender unit in place, unscrew the donut, and you are now looking into the fuel tank from the top.

Insert the drain tube, and start draining, when you are done, make sure you are cleaned up before you start putting the interior back together.

You can use syphon if you have the height, or an old fuel pump from a car, dont use thin hoses, this is a big tank and u need a thick hose.

Make sure you have enough fuel cans handy, and only attempt this when you are working with another person, 1 of you needs to break the syphon while one handles the hose.

when done, be very carefull to put everything back together just as you found it, do not leave anything loose or untightend, be carefull that the pushclips are properly pushed together, and the donut screwed on as tight as it was when you took it off.

and dont use the “inhale fuel” syphon method! use a priming pump or jiggle pump, both cost just a few quid, syphoning with your mouth is unhealthy, dangerous and tastes disgusting!.

I have included a picture of a tank on sale on ebay from a 7 series in The US, its the same set up, this shows clearly how the 7 series operates what is basiclly a two tank system, the only time when it is a “one tank” system is when you are filling it and the fuel pours from one to the other, they have 2 sets of flow lines, and 2 sets of return lines, and two senders, this is not too disimilair to the old jag set-up, except the old jags did have 2 tanks – becuase they hadent figured out how to fill one from the other – a problem bmw solved.

Good Luck



6 thoughts on “The BMW saddles”

  1. John Berrick says:


    This will be the worst you have ever read, I have a 59 plate E60 520d, I managed to fill up a completely empty tank with petrol!

    I thought that the nozzle of the fuel pump was not going in since there is something wrong with my fuel tank opening! ( now know its a protective thing)

    Anyway, I filled in slowly took me 20 mins, the Guy @ Shell also came to help out and never realised what is being done!

    This is with my car running now- I thought that some settings on I drive has shut the fuel cap off!

    So anyway 60 litres filled in with car engine running, I started driving, and very strange cracking noises were coming from underneath and with a burning plastic smell! And the car wont take a pic up, 2 days before this my friend had a similar kind of problem and he was told its a turbo failure, so I thought that the disease has spread to mine as well!

    I live about 15 miles from this Shell filling station and had driven 10 miles, when I realised what I had done – filled in unleaded!

    So done was done, I thought its a dead engine, came back home – it was midnight, googled and read all this, got a professional local guy, who came in the morning – drained my tank empty and restarted, the car ok!

    I was about to call BMW rescue ( but that would void my AUC cover plus the bill !)

    In all honesty, it might have done damage to the engine with

    a) Filling in with car running for 20 mins
    b) driving 20 miles back

    For now its ok, but will have to see in few months or coming couple of yrs how it will show out- ie the damage caused.

    So the bottom line is even with this protective mechanism which BMW fitted I never knew – this happens so often i.e. misfueling,

    Main thing is – eg my case is ironical and at the same time hilarious, but if someone learns and save their cars with this comment it is still helpful to mention on here,& get a professional to empty your car out for me he charged 150£ with about 7 litres of diesel added as well.

    I will post on if any fault comes up if coming months or even yrs, I love my car! So not getting rid of it so easily!

    Thanks to fuelfixer which is a wikipedia for misfueling.

    1. TheFuelMan says:

      Your welcome John, will be interested to hear how it is in a few months, fingers crossed!

      1. John Berrick says:


        Just one more thing, I live in Edinburgh, I called your number last night unfortunately the guy who covers Edinburgh area, is off this week, but I must say the gentleman I spoke to was so humble, professional and corteous, he kindly gave me another contact who works around in & around this area.

        This is a true nature & of not only running a business but following work ethics and going an extra mile to help ( in this case you helped me!), I will very strongly recommend Fuelfixer to everyone,

        One more thing if I can take your advice based on your experience, what would be your thoughts on the damage to my engine/fuel pipes etc with the history I have provided you.

        Any suggestions or opinions from you will be invaluable, given the experience you have. Would you advice me to go to BMW for just a general health check at all?

        I understand it wont be nice or ethical of me to ask ( that of-course I will not disclose the incident to BMW), but if you can give me some advice in any way or form I will be grateful.

        With Regards

  2. victoria edwards says:

    i have put 5 litres of diesal in my petrol daewoo lanos! is this ok ? can you help me? is my car going to break?

    1. TheFuelMan says:

      Hello Victoria,
      The daewoo lanos has a 40 litre tank, so 5 litres is about 12.5% of the capacity, Daewoos have a hardy little engine that can deal with a bit of diesel better than most , What you need to do is fill the tank to the brim with petrol and it will drive fine, what will happen is the diesel will not burn completely in the combustion chamber and it will slide down the piston, thru the rings and into the fuel sump, the net result is the engine oil level will rise and if left uncheckd – this will cuase problems becuase too much oil is bad, and oil thind with diesel does not have much lubricating qualities, so check you oil every 100 miles, if it rises more than 1cm above the max – get an oil change quickly, – other than that you should be fine and actually it will help clean out the oil ports and oil channels – good luck

      1. Ben Shepperd says:

        Many thanx for you help today.
        You done an excellent job.
        Ragards, Ben Shepperd.

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