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  1. #1

    Default Expansion tank - pipe identification

    Quick question: How many hoses are connected to a roadster expansion bottle and where do they go/come from?

    I have shoe-horned a 450 smart engine into a van and tried to use as many Smart bits as possible but having trouble with cooling. The roadster radiator (with the bleed on the top) and flatter expansion bottle look like they may make life easier. 450 bottle has loads of pipes connected that I don't think are needed. From ebay the roadster one only has 2? if one is flowing into the system to act as top up/expansion what is the other?

    Also how often do you need to bleed the radiator using the top valve?


  2. #2

    Default Re: Expansion tank - pipe identification

    The roadster expansion tank has 2 pipe connections.
    The lower one feeds coolant into the engine. The upper one I believe is an overrun exit. Not sure where it goes.
    The bleeder on the radiator is only used when replacing the coolant.

  3. #3

    Default Re: Expansion tank - pipe identification

    Thanks Bjorn

    Its where the over-run pipe comes from that interests me.

    Ideally I would want to just use the fill pipe and cap the other outlet off, but don't want to trap air anywhere if i don't have the over-run connected.

    Anyone got any ideas where this pipe connects to?


  4. #4
    Join Date
    Dec 2016

    Default Re: Expansion tank - pipe identification

    If it's a somewhat normal system then the 'over-run' is an overflow connection from the atmospheric side of the pressure cap. The pipe from it would just run down under the car so that in the event of the pressure forcing the cap open, such as on overheating, the steam and liquid discharged is not blasted into the engine bay.

    If that's what it is you certainly shouldn't block it off - it's basically a safety valve outlet.

    Edit: A bit of googling for diagrams suggests that (if not the above) it is probably a secondary feed or a bleed pipe, in which case it would go to a tapping in the top of the radiator or engine. If neither your rad or engine have a tapping to accept that then you can't use it, so block it off. As yours is an oddball installation presumably the piping is all non-standard, so it's going to be trial and error on whether you get trapped air.
    Last edited by dpmike; 23rd August 2017 at 19:44.

  5. #5

    Default Re: Expansion tank - pipe identification

    Thanks. It's not on the atmospheric side of the pressure cap but is above the water line in the expansion tank. I don't think it's from the rad as that only has flow and return from what I can see on eBay images. I have the engine from a Smart City Pure so it should be a similar set up.
    Just really need someone with a roadster to have a look and see what it connects to if possible.

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