Varga / Shinn VG-21 Squadron

MAINTENANCE ITEM #2

*** HIGH ENGINE OIL TEMPERATURE ***

By Lee Beery

Several Varga owners have just recently reported high engine oil temperature. I have experienced this problem myself and now believe I have the riddle solved. If your Varga oil temp runs over 200 constantly, do the following. Note what the oil pressure is when the oil temperature reaches 200 to 220 degrees and make the same notation when the oil temperature peeks. If the pressure remains at the same basic pressure, +/- 5 PSI and still in the green, the engine is still being lubricated. To verify the gauge is functioning properly you can remove the temperature bulb from the rear of the oil filter/screen housing, immerse it in water, heat the water until it boils. (I used a one-cup submersible heater used in travel kits for making coffee.) The cockpit gauge should indicate 200-210 degrees. Next, inspect the engine baffling for being in good condition and flexible. Fill all gaps with "RTV" sealant. Make sure the baffling on the rear of engine is bent forward and bent in on the sides. Next, make sure that the most inboard opening on the left side, rear baffle, has a short piece of scat cooling hose directed right at the engine oil filter/screen housing. Most Vargas I have looked at do not have this cooling hose properly routed. It is important that a blast of air be directed at this point on the engine. The cooling hose running between the rear baffle right side and the oil cooler was increased from 2" diameter to 2.5" on Vargas 79 and up. (So you see, George Varga knew there was a heat problem.) This also requires a little more effort as it requires rework of the oil cooler shroud and the engine rear baffle. Also at this time, be sure the most outboard ducting on the rear baffle left side is connected to the cabin air control box, center top of firewall, for summer operation. I suggest you now go fly and see if you still have a problem. Chances are it's a little better but still above the 245 degree mark Lycoming would like to see.

At this point, I replaced the flex hoses and sent the oil cooler out for cleaning. This also helped a few degrees. This means the culprit could be the thermostatic oil cooler bypass valve. Chances are you have a P/N LW10269 valve. If the valve face is worn, (ours was bad), or the wear pattern is not even, it will not close properly, allowing oil to continue to circulate through the engine lubrication cavities rather than being routed through the oil cooler. All this information can be found in Lycoming Service Instruction #1255 and #1316A. It is also possible that the valve seat located in the rear case is worn to the point a new valve will not solve the problem. Lycoming has a rework that can be accomplished on the valve seat, but this would

require engine removal. The most cost effective fix would be to replace the oil screen housing assembly with an oil filter housing which does away with the valve seat in the engine rear case.

By all means use the correct summer weight oil, change it often and keep the quantity up where it belongs. You can't cool the oil if it's not there. Don't allow grit and grime to collect on your engine or let oil leaks go unattended.

I am grateful to the Lycoming Representative located at Carson City, NV for their assistance with this problem. If you have a problem with your Varga/Shinn, now is the time to let it be known - it could be the subject of our next Newsletters.

The illustration shows the differences in construction of the thermostatic oil cooler bypass valve P/N 75944 and it’s alternate P/N LW-10269.

It has been determined that the alternate valve LW-10269 does not function properly in some instances. It is recommended that the thermostatic bypass valve LW-10269 be replaced by 75944 immediately if high oil temperatures have been encountered or the next 100 hour inspection to forestall an possible future high temperature malfunction.

P/N LW10269

P/N 75944