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Oil cooler installation

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PTAirco

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My O-300 engine has had an oil cooler installed sometime in the distant past. A very experienced IA today pointed out something which he thought was curious: an oil line comes from the top of the engine from the oil gallery and continues back to the oil cooler.
The oil goes through the cooler, presumably under pressure, and exits back into the engine sump. His concern was that the oil being simply dumped back into the sump would reduce oil pressure overall in the system. Generally my oil pressure is very high at startup, almost redline, and within a few minutes settles down into the yellow arc. At full power it goes into the green. And then after a while at cruise, it settles back down at the high end of the yellow. This is a 1965 gauge, so I have no idea about its accuracy and I know it could be made to read anything according to how the relief valve is set.

I'm not sure if this oil cooler arrangement is in any way unusual. There would have to be some pressure differential to force the oil through the cooler, no?
 

TFF

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I don’t know Continental engines well but that is an odd routing if it’s correct. Is there a 337 in the records? Might give direction. There has to be a Vernatherm to keep oil pressure from busting the cooler. Are you sure it’s into the pan and not back into the oil galleries through an external port? My guess though on the oil pressure is the time on the engine. Does it have a good chunk of hours? Sounds like wear clearances are wide. It’s not hurting it’s self.
 

PTAirco

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I'll have to investigate further next week. It has about 800smoh. Runs great, doesn't burn much oil.
 

TFF

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I’m sure it’s fine from a safety standpoint. I would go for a ride.

This is not a knock because it is what I got, but field overhaul after field overhaul leads to be a loose engine. In spec but not ideal. Broad broad statement. I had my engine crank reground. It was in spec for standard bearings, right at the loose limit. That is what the previous OH had done. Throw STD bearings in. When they sold it they could claim std crank. That is only a hair from the tight side of .003 undersize. For .003 undersized they polish it to that spec. Grinding machines can’t do .003; nothing there to play with. There was other problems with my crank that added up to to the work being done, but being a field overhaul it was perfectly in spec to throw standard bearings back in or have it polished and throw the .003s in and it’s overhauled.

My bet is the cooler goes through an external loop back to the galleries.
 

Toobuilder

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I'm having a hard time thinking that the cooler is fed by a main galley and then dumps into the pan. That would be a HUGE oil leak that the oil pump could never keep up with. If that is indeed the fluid circuit, then look for a pill restrictor in the outlet leg of the cooler.
 
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Toobuilder

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Of course if the flow is restricted enough to maintain oil pressure then it's not helping much in the cooling department. Weird.
 
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