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Looking for suggestions or how others route the oil return line back to the oil tank.  Been having issues with the fire sleeve showing signs of heat and cracking after about 25 hours.  Replaced the fire sleeve a few times already.

Tried different types of sleeve with the latest being the higher heat silicone type and that one is starting to do it.  Can't really get it any higher -- there is visible space between the sleeve and the area above the exhaust manifold.  I attached a picture before the first time it was changed and you will see the heat damage.

It is a rather tight cowl (Sling 4) and that area above the manifold must not get enough air flow.  The line routes directly over the manifold to the right side of the airplane where the oil tank is mounted to the firewall. 

Cowl modifications to direct airflow in this area?  Heat shielding?  Reroute to the left and somehow loop all the way around the engine?

How do others route this line?

 

9748_1_IMG_0709.jpg (You do not have access to download this file.)
  • Re: 914 Oil Return Routing

    by » one year ago


     

    Try this fix -(writen for another discussion):

    You can make your own custom fit. light weight, low cost, shielding -

    I use malleable aluminium "flashing" which you can get from any hardware store - comes in a role.

    Purchase a role of exhaust wrap and a tube of high temperature silicone - automotive store.

    Measure the length of hose/tube you want to protect & diameter of the tube. Cut a slightly oversized piece of aluminium (HD/workshop sizers/shears will do the job).

    (The Rotax diagram infers protection over the whole length of hose - this is usually unnecessary - targeted protection will save weight and cost)

    Cut sufficient strips of exhaust wrap to cover the exact length/diameter of pipe - when laid side by side, on the aluminium, there will be a small uncovered margin on three sides.

    (Good idea to wear disposable gloves from now on.)

    Wipe one side of the aluminium with isopropanol/carburettor cleaner/mentholated spirits to remove any grease/contaminants.

    Using the HT Silicon, liberally cover each strip of exhaust wrap and lay side by side on the aluminium - press firmly onto aluminium & leave over night to cure.

    You now have a high temperature shield than can be bent/curved over the hose (exhaust wrap on the inside) and secured in place with sufficient double wrap safety wire or metal zip/cable ties.

    If your measurements/cuts have been accurate, the shield will slightly overlap, along its length, helping to keep it in place. 

    The shielding can be reused as many times (5 year rubber replacement) as you deem fit.


  • Re: 914 Oil Return Routing

    by » one year ago


    Lots of heat going to the right. If you go to the left side with a longer hose routed to the rear and then go right you can avoid much of it but it will take longer to get a burp


  • Re: 914 Oil Return Routing

    by » one year ago


    Sam Purpura wrote:

    Lots of heat going to the right. If you go to the left side with a longer hose routed to the rear and then go right you can avoid much of it but it will take longer to get a burp

    Be careful of the resultant bend radius kinking the hose.

    Oh! and a longer hose is very unlikely to change your time to "Burp",  just add a little more to the total oil volume (not a bad thing)


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