Can someone please explain the purpose for the rubber pad under the expansion tank?  There is nothing within over an inch from the bottom of the tank.  Is this an artifact from the ULS that got carried over to the iS?  It’s even on the 5-year rubber replacement list.  Just question the value in replacing it.


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  • Re: Expansion Tank Rubber Pad

    by » 3 months ago

    Hi Bob

    Yes indeed it is an artifact from the original 912 engines where it would bounce on the top of the crankcase in some installations.  Depending on how the hoses support it there is always the risk that someone will not check that area and it could be mounted incorrectly and come in contact with the block.  (generally on start and shutdown the engine "shake" can sometimes do it)  The iS is very unlikely due to the repositioning of the tank more forward from the carb versions.  


  • Re: Expansion Tank Rubber Pad

    by » 3 months ago

    Thank you very much for the validation.  One less item to have to worry about replacing.

  • Re: Expansion Tank Rubber Pad

    by » 3 months ago

    They were installed so there wouldn't be any contact between the expansion tank and engine cade. I see many where the rubber loops are broken and the rubber pad slides out if position. I used to replace them, but now I use a good silicone adhesive on the bottom to keep it in place. I clean both surfaces with Lacquer thinner first. I've  never had a pad come lose. I do agree some tanks are up off the engine, but sometimes I see a hose change cause the expansion tank to dip too close to the engine.

    Remember two things. Bettersafe than sorry and an ounce of prevention is worth a pound of cure. 

    Takes 2 minutes to secure the pad and possibly keep you safe.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

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