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I have a 1994 912UL 80hp that I am running and seems to be having increased oil temp issues. The temperature doesn't rock up but the report I got was that it sat around 250 for a little then began to move higher past 270-280 after about 20 minutes of flight. The plane landed shortly after cause of this to limit any heating issues.

A few notes about the flight:
Temperature was a cool Sunday morning maybe 60s.
Ground WOT 5100
Cruise around 5000 +/-100 RPM
The plane does not have a Oil Cooler (Is this a required item?)
I want to say the WOT Cruise speed was just around 5500 but I can't confirm.
This was the first time it was flown in 21 years.
I think this was a known issue by my grandfather (Builder) as he bought a second oil temperature gauge and purchased a oil cooler but never installed it.
I know my gauges are correct cause I checked them with a temperature gun.
Water temps do not look to be incredibly high compared to the oil temps.

Questions:
If my oil is over filled will it cause foaming and increased temps? (wasn't there a change to the dip stick?)
Is the oil cooler required on the 912UL?
I may be slightly over pitched can this cause this sever of over heating?
Can old coolant be a issue?
Cowling slots to small?

Any thoughts or ideas are appreciated.
  • Re: Oil temps high, are Oil Coolers required?

    by » 6 years ago


    I don't know if they were required but my brand new trike with 100 hp. has one. I found it 100 percent necessary to Burp my engine before i check the oil. The old dipsticks from what i heard didn't sit correctly and could give false readings. They have pictures on the net of how to identify the old dipsticks. I saw pictures of an oil reservoir that was so full of crud (bottom) that would be something to take a look at and make sure no restrictions in the oil lines. Im curious what your WOT Rpm was at climb out.

  • Re: Oil temps high, are Oil Coolers required?

    by » 6 years ago


    Roger thanks for the response.

    I am wondering if people have any pictures of their coolers or there is some cooler installations people have documented.

  • Re: Oil temps high, are Oil Coolers required?

    by » 6 years ago


    Install the oil cooler. Look in the 912 Installation manual. The oil hose from the "out" fitting is the one that goes into the oil cooler. Then the out side of the oil cooler hose goes into the oil pump housing. Use at least 13mm (1/2") ID hose and it should be in fire sleeve. Don't use cruddy Ace Hardware garden hose serrated worm drive clamps. Use something better. Try to put the cooler in direct air flow.
    Over pitched prop will cause higher temps, but from your numbers you are not over pitched.
    The oil dip stick was changed to reflect a higher level in the tank. The old dip stick had a rounded end and the newer one that came out many years ago is more square. No you can't hurt anything if the tank is a little too full, but you could puke it out the vent tune all over.

    You really need to download and follow the Installation, Operator's and line Maint. manuals.

    Use the proper oil Most use Aero Shell Sport Plus 4. You can cause issues using the wrong type oil
    If the coolant is old drain it and install some new DexCool 50/50.

    Poor air flow through a cowl can also cause retained heat.

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


    Thank you said by: Al Creigh

  • Re: Oil temps high, are Oil Coolers required?

    by » 6 years ago


    I would highly recommend taking the Rotax line maintenance class. They scattered around the country. It is well worth the time and money, you will learn how to get the engine to TBO. From what I have seen a lot of the Rotax 912 issues are owner induced.

  • Re: Oil temps high, are Oil Coolers required?

    by » 6 years ago


    Roger,

    Thanks for the response here is what I am going to replace my coolant with. I am unsure if my grandfather put in 100% coolant or not but my current plan is to change out the coolant with the bellow, purchase the Oil cooler bracket from KF for the 912 and install a Earl's 7 blade oil cooler and see where that gets my temps. Will report back soon.

    https://www.homedepot.com/p/Prestone-128-fl-oz-DEX-COOL-50-50-Antifreeze-AF850/206382376

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