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Touring Motor Gliders Association (TMGA)
discus239

Oil Temp

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discus239

Sometimes during a long climb in hot weather oil temp will creep into the 220"s, then I will level off, reduce power and let it come back down.  I was wondering what relative wind the intake was seeing, so the other day temp reached 223-224, I pulled the cowl flap knob out about half an inch. Temp immediately responded, and in a minute or two went down to 213, no other changes made. Weird, looking at the angle of the door on the ground it is tilted toward closed quite a bit. Can't explain it, maybe someone else can .

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mikeschumann

My oil temp is consistently a LOT lower than that.  It sounds like your cowl flap is not open all the way.  When it is full open, it should be perpendicular to the cowl opening, totally parallel to the air flow.  The cable may need to be adjusted if this is not the case.

NOTE:  The cowl cable needs to be well lubricated periodically or it can be difficult, if not impossible to open the flap after it has been closed.  I use a cable lube tool that you can buy at motorcycle shops, which clamps over the end of the cable and lets you force WD-40 into the cable.  It's a messy affair and takes a significant amount of lube before it comes out by the control knob in the cockpit (make sure you have a rag properly positioned or you will make a big mess).

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discus239

Thanks Mike, when fully open it is correctly perpendicular, it runs cooler when partially (like 20 degrees) closed. Temp only climbs after a long 4-5000ft. + climb so doesn't occur often, I lube the exposed end of the cable and so far always smooth, will perform further analysis.

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mikeschumann

What is the outside air temp and your airspeed when you run into this?  Jim Lee suggested that when you start running hot, you increase your airspeed, which obviously will increase the airflow thru the oil cooler.

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Eric Greenwell

I hope I remember to try partially closing the flap the next time I make a long climb. Could be 4 months before the weather is hot enough to be a problem, and I might forget by then 😉

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Jim Lee

Hey Discus 239, that you Bill?

What you describe is common.  What Mike said about the cowl flap position is correct.  What happens is the cowl flap cable slips in the clamp.  It is attached to the radiator cowl with a clamp.  When the cable housing slips in the clamp, the cowl flap setting changes.  Yours now allows the cowl flap to go beyond open to a partly closed position.  If you take a careful look at the cowl flap in full open position (I know that you already did, but imagine the tail sitting 2 feet high in the flight position) and imagine the air flowing straight into the inlet, you will notice that the partly closed cowl flap will now disrupt the airflow, decreasing cooling.  Pull the cowl flap out one notch and see if the angle looks better.  It doesn't take much of an angle to make a big difference in oil temp during the climb.

Two easy fixes.  Number one, pull the cowl flap knob out one notch and look at the cowl flap position.  If it s now in the full open position, then this is your new open position of the knob.

Number two, measure how much cable movement it takes to put the cowl flap in the open position.  Remove the lower cowling, and move the cable housing this amount in the clamp.  Your open setting will now be correct.

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