Is my oil cooler doing anything??

[MikeOH]

I've had my '70F for over 7 years and the oil temp has always run hot.  220-230 in the summer and 200-210 in the winter.  Below is from a flight a few days ago and you can see it 'stabilizes' at 208.  Over the years I've replaced baffles, overhauled the oil cooler, replaced the oil cooler lines, and the vernatherm.  ALL to NO avail

You can see the vernatherm actuate at right around 180, like it should.  But the temp then just keeps right on increasing!

Any ideas on how to determine if any oil is actually FLOWING through the cooler?  I'm beginning to wonder if that is the problem.

 

[Ron McBride]

Talking to Paul Löwenstein-Jensen, in testing Lasar found the air thru the stock oil cooler came thru the cowling top and then out the cooler.  Sounds illogical though.   I install the relocation cooler kit and a new cooler in my 69f, this helped a little, but the engine was getting past 1500 hrs.  I have sold the plane and do not have recent information.

Ron

[MikeOH]

41 minutes ago, Ron McBride said:

Talking to Paul Löwenstein-Jensen, in testing Lasar found the air thru the stock oil cooler came thru the cowling top and then out the cooler.  Sounds illogical though.   I install the relocation cooler kit and a new cooler in my 69f, this helped a little, but the engine was getting past 1500 hrs.  I have sold the plane and do not have recent information.

Ron

Thanks!

What were your oil temps before/after the relocation?  (If you recall)

[takair]

Is this the stock oil temp location?  Do you still have the original gauge and does it match the digital?  Do you have the little metal shield between the exhaust and the cooler lines?  

I have seen between 170 and 220 over the years.  170 on coooold days.  220 on hot days, down low with higher power.  It runs a nominal 180. At one point I sealed the top and bottom of the oil cooler to keep air from spilling passed.  That seemed to help on the hot days.

[MikeOH]

33 minutes ago, takair said:

Is this the stock oil temp location?  Do you still have the original gauge and does it match the digital?  Do you have the little metal shield between the exhaust and the cooler lines?  

I have seen between 170 and 220 over the years.  170 on coooold days.  220 on hot days, down low with higher power.  It runs a nominal 180. At one point I sealed the top and bottom of the oil cooler to keep air from spilling passed.  That seemed to help on the hot days.

Yes, and the factory gauge agrees with my digital (Insight G3).

Yes, the heat shield over the oil lines is in place.

I've NEVER seen below 200 regardless of OAT.

Good idea to seal the top/bottom/sides!

You did give me an idea of how to test if my cooler is providing any cooling: I can block it, take a flight and see if it is any worse!

[takair]

Just now, MikeOH said:

Yes, and the factory gauge agrees with my digital (Insight G3).

Yes, the heat shield over the oil lines is in place.

I've NEVER seen below 200 regardless of OAT.

Good idea to seal the top/bottom/sides!

You did give me an idea of how to test if my cooler is providing any cooling: I can block it, take a flight and see if it is any worse!

Good thought…..maybe do 1/4 at a time using aluminum tape just to be sure you don’t overshoot.  I’ve done that when really cold….

[MikeOH]

2 minutes ago, takair said:

Good thought…..maybe do 1/4 at a time using aluminum tape just to be sure you don’t overshoot.  I’ve done that when really cold….

Good point!

Going 'whole hog' might end badly

[takair]

One other thought, I know you replaced baffle seals, but be sure that the lower forward seals to the cowl are good.  There are often big leaks around the starter and alternator.  These leaks could have an impact on oil cooler flow even more than the cylinders.  These are harder to see if you have a cowl closure, but would still be a leak…. What are your cylinder temps?  I would expect an F to be under 350.

[MikeOH]

6 hours ago, takair said:

One other thought, I know you replaced baffle seals, but be sure that the lower forward seals to the cowl are good.  There are often big leaks around the starter and alternator.  These leaks could have an impact on oil cooler flow even more than the cylinders.  These are harder to see if you have a cowl closure, but would still be a leak…. What are your cylinder temps?  I would expect an F to be under 350.

Great suggestion!  I've never looked closely at the seals around the lower front.

#2 has always run hotter than the others (I would expect #3 to be the hottest) at around 350-370 in cruise depending on OAT.  It will go above 400 in a climb especially on a hot day; sometimes have to reduce power to keep #2 under 410.  The others are low 300s in cruise and well below 400 in climb, 360-380.

[McMooney]

question, back in my ol hot rodding days, we'd want the oil in the 200 - 220 is range,  why is it different for aircraft ?

[EricJ]

2 hours ago, McMooney said:

question, back in my ol hot rodding days, we'd want the oil in the 200 - 220 is range,  why is it different for aircraft ?

Lycoming and Continental engines are air-cooled (and oil cooled), and the oil temperature is taken as it comes out of the cooler and is entering the engine lubrication paths.  Automotive engines often don't have separate oil coolers since they're usually liquid-cooled, and the oil temp is often the temp of the oil in the pan.   

In both cases the oil needs to get to around 200F to remove any water at low altitude, and in airplanes it typically hits that in the bearings, heads, or on the back of the piston, cylinder, etc., before it returns to the sump.  The cooler removes some of the heat so that the oil can absorb more as it goes back through the engine.    Also, since the boiling point of water drops with increasing altitude, the water will come out at lower temps at altitude than it will on the ground, so it isn't quite as critical to stay as hot for that purpose.   Other than that it mostly just needs to stay warm enough to circulate easily and maintain sufficient pressure for the bearings.