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Ineffective Oil Cooler on O-200

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Marc W

Well-Known Member
Joined
Mar 31, 2017
Messages
1,234
Location
Colorado
A friend has a bit of a puzzler. He has a Zenith 601 with a Continental O-200. He bought the airplane in coastal Alabama. He winters there. He few it there and oil temperatures were good. He left Alabama in the spring to fly the airplane to western Colorado. He didn't make it far. One of the rocker pins came adrift and wore itself through the valve cover. Engine didn't like that and he made a forced landing.

He had the engine rebuilt and repaired the airframe damage. The engine rebuilder installed different pistons to make a claimed 118 HP. My friend flew it in the southeast for a while and said oil temps were normal. He started west and started having high oil temperature problems over New Mexico which have continued.

He installed an oil cooler adapter under the oil filter and installed a nine row oil cooler. The oil cooler adapter is on the left side of the engine and he hung the oil cooler on the right side of the engine so there is a good three feet of AN6 hose coming and going. He originally had a 2" scat hose feeding air to the cooler off the baffles on the right side. The oil cooler didn't help at all. He then replaced the oil temp sender. I suggested he run a 3" scat hose instead and he did that. He tested it today and it didn't make any significant difference. Hard to say if it helped because conditions were not the same.

He doesn't have an ideal setup. The scat hose first makes a 30 degree bend downward from the plenum and then makes a 90 degree bend to enter the cooler. He has at least 6' of AN6 hose connecting the cooler to the adapter. Also elbows on the adapter and the cooler. Not an optimum setup. Even so, it seems like the oil cooler should help some.

The oil cooler adapter has a pressure relief spring that bypasses the cooler when oil is cold and oil pressure is high. It sends oil to the cooler when the oil warms and the oil pressure drops. I am suspicious of that unit also but he claims they checked it.

It may be a perfect storm of poor airflow to the cooler because of the bends in the scat hose and to much AN6 oil hose with to many 90 degree elbows. Also the higher density altitudes here. However, I am wondering if there something that could have happened inside the engine to dump more heat into the oil? Incidentally CHT's are fine, somewhere around 300 degrees.
 
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