Open Breather System...Fuel smells

Discussion in 'How To' started by PanZer, May 8, 2018.

  1. On a type 4 engine (1700,1800 or 2.0l) the breather is a box (vapour trap) on top of the crankcase, on a type 1 (1600) it’s off the oil filler pipe. The slight vacuum in the air filter helps remove the combustion fumes from blow-by and reduces oil contamination. Type 4 engines don’t need rocker cover vents as the breather works reasonably well but some Type1 engines do because the standard breather is barely adequate.

    There is no advantage in venting either the fuel or crankcase breathers direct to atmosphere; it’s bad for the environment and makes the crankcase breather much less effective.
     
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  2. Great! Thanks @77westy
    That's cleared some things up and narrowed other things down.
    Since mine is a boarded out and modified 1600cc, the Crankcase Breather is on the Oil Filler tube. Currently that vents to the RHS Carburettor Air Filter (LHS one doesn't seem to have an inlet...
    [​IMG]
    (It hasn't been done very well so could do with changing anyway)

    Another option for the Crankcase Breather is this K&N style Filter @ £12...
    [​IMG]

    The above would free up the inlet to the RHS Carb Air Filter for attaching my Fuel Vapour lines to...which would mean I don't have to drill through the tops of the Air Filter caps to attach connectors. I don't mind doing that but if there is a more elegant solution I'll take it.

    A 3rd option is to get a Breather Box @ £45...
    [​IMG]
    (Might be hard for me to install without help getting the engine out the way)

    I think it has about 5 in/outlets to utilise.
    1 for Crankcase/Oil inlet
    2 for Fuel Vapour Lines inlets
    1 outlet for Breather Box to RHS Carb Air Filter inlet
    The 5th could go god-knows-where (I've read such things as "valve covers" & "gen stand" but haven't a clue what those mean) or to a K&N style Filter like the 2nd pic. Capped even!

    Final option, unless a combo of above is best, is an Oil Breather Tower (not EMPI brand) @ £110, which brings with it easier oil pouring...
    [​IMG]

    Several outlets again:
    1 to K&N Filter if it's ok to keep Carb Air Filter free for Fuel Vapour Lines. Others can be capped or connected to God-knows-where!

    I don't mind drilling in to the Carb Air Filters, as that was the original plan for the Fuel Vapour System. Just exploring options.

    Many thanks all. Just hoping that a solution can bring with it safety and not hinder performance.




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  3. Baysearcher

    Baysearcher [secret moderator]

    That little filter won’t provide the negative pressure your crank case requires.
     
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  4. Cool. Thanks. Heard the pressure was important.
    I’ll cross that off then lol


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  5. Baysearcher

    Baysearcher [secret moderator]

    I’ve never been convinced those breather boxes do anything either, baring in mind it’s just an empty metal box.
    Do it as VW did. They tended to know what they were doing!
     
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  6. Yeah, I’ve read to keep things ‘as it was’, but the engine itself isn’t ‘as it was’; with twin carbs and bored out to 1950cc it now does 80mph and revs @ 4000rpm, so I’ve heard some further modifications are required to compensate for that.
    I’ve no clue myself though as I’m not a mechanic. For every opinion and argument there is a counter one that sounds just as sensible to me


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  7. Merlin Cat

    Merlin Cat Moderator

    Sorry for jumping on your thread @PanZer but I also get fuel smell (even before current problems) and seem to have open ended pipes in my engine bay that I don’t understand.

    Does anyone know if it makes any odds if your engine was originally fuel injection and is now twin carbs?
     
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  8. I also have no proper fuel tank breather vent system, mines a jurgens so was hacked about from new and has two fuel tanks, however, the breathers from the tanks run up into vents with just a bent over bit of thin hosepipe.

    Ive been looking for a breather solution for a while and best seems to be to make something up out jiic type fittings with a one way breather valve and then to an air filter.

    My only concern is where does the tank breath IN from? if the breathers are attached to something that sucks (the carb) are they breathable fuel caps? Or is the pressure from the carbs so little that it would allow air back into the tank to replace the space where the fuel was as the engine drinks it? Hope that makes sense?
     
  9. Interesting point!
    I know my fuel cap is not a ‘breather’ one. My guess is the air in the fuel tank is not much of a consideration as when filling up whatever air is in there will be forced out through the Vapour System and Filler Pipe.
    From my reading air becomes more of an issue when it is once again a ‘closed’ system (Fuel Cap back in place)...especially when temperature rises as this causes the Fuel Vapour - hence a system to deal with that.
    With our non-existing Fuel Vapour Systems the fumes just go to the end of the Pipe work (whatever that may be lol)...hence smells and potential fire hazard.
    Everything I’ve read and been told says to take the Fuel Vapour Pipes to an Air Filter (the original single one on a standard setup)...in my case one above my Twin Carbs.
    Now, as you say, can this then suck all the air out of the fuel tank?! Lol Considering it is a suggested option for us a blimmin well hope not ha ha
    The Oil/Crankcase Breather goes to one of my Air Filters so perhaps it isn’t an issue.
    I really have no idea what I’m talking about though


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  10. @Merlin Cat here's the diagram from ratwell, a FI bus would have originally have had breathers venting into the air box. If (like mine) the fuel injection gubbins and air box is long gone and you're now on carbs the breathers all still need to be connected up and plumbed into one of the carbs (ie the bit from the "T" piece in this diagram). My breathers were fine over the top of the fuel tank but missing on the left hand side behind the spare wheel tub, and missing over the top of the engine bay also. It was one of the first jobs i did, not hard, just get some tube and connect it all up with suitable clamps.


    [​IMG]

    here's where mine vents in to the top of the RHS carb air filter (i had to drill the hole):
    [​IMG]
    Breather
    by Rob E, on Flickr

    On the t'other side of the air filter top plate i drilled through the fixing and added some lock wire so there is less of a risk of something falling into the carb:

    [​IMG]
    Breather
    by Rob E, on Flickr

    hope this makes sense?
     
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  11. As @rob.e has done, I've read to place the pipe connector on the Carb Air Filter 'off centre'. Not sure what the voodoo magic rational is but I'm gona do just that.
    Seems I have a solution to implement, so time to start ordering pieces


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  12. Yep, it's off centre for a reason.. i have absolutely no idea what the reason was but there definitely was one! :)
     
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  13. This^:thumbsup:
     
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  14. Do you mean that because the engine now has carbs it doesn’t need the breathers connected? I think you have the crankcase breather open to the engine bay so the fumes will simply be sucked into the engine cooling fan and the heater – assuming you still have the heat exchangers – and be pumped into the cabin. If the fuel tank breathers are also open they’ll be venting wherever the pipe ends – probably at the top of the engine bay – and will also be sucked into the fan and heater.

    The VW breather is a basic and simple system that works reasonably well; reducing engine oil contamination and increasing engine life also reducing unburnt hydrocarbons released into the atmosphere. Both the crankcase and fuel tank breathers should be connected to the air-filter(s).
     
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  15. What are the further modifications that you’ve heard are required?
     
  16. Merlin Cat

    Merlin Cat Moderator

    Ah, that’s why any passengers complain it smells of petrol in The van! I may be a bit immune to it :)
     
  17. Nope, it’s slowly killing you.;)
     
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  18. Merlin Cat

    Merlin Cat Moderator

    :eek:
     
  19. The guy I bought mine off (hard to tell what were exaggerations, lies or truths from him really) told me he also upgraded the breaking system, suspension and something called a Heavy Crank, to suit the more powerful engine.


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  20. you probably have the upgraded blinker fluid too
     
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