also worth saying, this works, but this solution has the risks mentioned at the bottom which the original valve does not have.
further, also note that what this approach fixes is the secondary vent which had also got blocked. the main tank itself has a vent, shown below:
this vent has the exit next the the fuel filler cap, pipe shown from inside as below:
So this must be blocked as well. but its too difficult to remove as the valve is on the top side of the tank. thus my approach to get the secondary vent on the expansion tank sorted.
first remove the rear right wheel and mudguard trim:. pull out the plastic clips shown below, there were 6 of them plus screws holding it in place:
These clips were non-reusable, so i picked up new stuff from ebay. easy enough and cheap enough (£2.99/10 units or so). link below:
http://www.ebay.co.uk/itm/270818154580? ... 167wt_1110
next remove the expansion tank, which you see when you look up through the mudguard, its held high up, with 2 nuts and bolts. when you remove the 2 nuts it hangs out like below, from the pipes. tank when empty is not heavy so don't need to worry about pipes bending due to weight:
the blocked valve is the one in white. check blowing into it/sucking (with the fuel filler cap off), and if no air passes either way you know its blocked.
ideal solution is to replace the valve, but the valve comes with the expansion tank itself so you have to replace the whole tank.
alternative solution is to drill a vent hole at the TOP of the tank, as below:
1. drill a hole (well, i did 3 just to make sure!!):
now if you blow into the new hole or suck air out, you should feel air movement through the fuel tank filler hole. that should indicate to you that the vent is working.
2. covered it up nicely with a 2-layer fabric filter, glued in place and duck-taped as backup:
Fix everything back in the reverse order. all done.
This solution puts a hole (no flow control) where originally bmw had a one-way valve (outflow only, no inflow) that too the outflow was controlled by a float valve. the original design accommodated 2 situations that the hole doesn't:
1: in case the car went belly up, the float was designed to close, not allowing diesel to leak.
2: if the car went in that much of water (vent tank is held as high as or above the fuel filler cap, so if i went in water that deep), the valve wouldn't have let water in, the holes will.
both of these i don't have a problem with. but thing worth considering if resorting to this solution.
also given that these cars have a primary vent from the main tank and a secondary from the expansion tank nobody knows how many cars are actually running with one of them blocked.. cos you'll never know untill both of them get blocked!
lets hope none of you have to go through this!
