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High oil temps and a "reversed" oil cooler plate

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triwayne

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I am starting to see some high oil temperatures in my RV-6 (O-360 A4A). Usually they are 185-200. The past few flights I saw consistent 225. I removed the vernatherm and tested it several times. It opens at 185 like clockwork. However, it is an old version and I ordered a replacement as per lycoming.
I have been reading several threads with similar issues. It seems that airflow through the cooler is a major issue.

I have attached pictures of my existing setup. There is a 3" tube running from top of cyl #3 to oil cooler. There is a cold weather block plate that is controlled by a cable on the console. It seems to me that the block plate is pivoting in the wrong direction and that, when opened, is impeding air from flowing through the cooler.

Here is what I'm thinking to do to solve the problem:
1 - install the new louver kit

2 - remove existing cold weather pivot plate.

3 - build & install fiberglass channel from bottom of oil cooler and ending at top of louver. (Do I need to add downward facing louvers to this channel?)

4 - replace 3" tube with 4" tube.

Thoughts? ideas?

Thanks in advance! - Wayne
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triwayne said:
I am starting to see some high oil temperatures in my RV-6 (O-360 A4A). Usually they are 185-200. The past few flights I saw consistent 225.
Click to expand...

Wayne, is the airplane new to you?

The baffle-to-cowl seals are a mess. Mass flow through the cooler and through the cylinder fins is a function of pressure difference between the upper and lower cowl volumes. Very leaky seals like the ones in your photos reduce that deltaP. I suspect your CHT numbers are a bit high too. Replace the woggly seals with some properly fitted silicone seals

I can see leaks at the oil cooler inlet diffuser (if we can call it that). Some RTV would help there.

A 4" scat may be worth considering. You can increase deltaP across the cooler by ducting the outlet to a region of lower pressure, so consider it too if you like...but I'd fix the fundamental stuff first.
 
DanH said:
Wayne, is the airplane new to you?

The baffle-to-cowl seals are a mess. Mass flow through the cooler and through the cylinder fins is a function of pressure difference between the upper and lower cowl volumes. Very leaky seals like the ones in your photos reduce that deltaP. I suspect your CHT numbers are a bit high too. Replace the woggly seals with some properly fitted silicone seals

I can see leaks at the oil cooler inlet diffuser (if we can call it that). Some RTV would help there.

A 4" scat may be worth considering. You can increase deltaP across the cooler by ducting the outlet to a region of lower pressure, so consider it too if you like...but I'd fix the fundamental stuff first.
Click to expand...

Dan wrote exactly what I would have written so I will simply say start with these 3 things and see what the result is.
 
The original builder of my -6 with an O-360 placed the oil cooler in the same place, using a similar duct to cooler transition. I had oil temp problems also along with higher than desired CHT?s. I enlarged the duct to 4? and made a fiberglass transition that smoothly goes from the cooler shape to a 4? diameter for the duct. I also used sceet which has an inner wall that is quite a bit smoother than scat. That combined with fixing those baffle seals as Dan suggested, will go a long way.

On hot days, 90 degrees plus, my oil temps and CHT?s are good.
A previous owner had 2 vents on the bottom of the cowl, which I now have blanked.
 
Thanks for the suggestions so far! I am a relatively new owner of this airplane. It had ~100 hrs TTE and airframe when I got it in late 2018. I've put ~70 hrs on it so far.. mostly in temps below 75. I'm in Southern VA and it's been in the mid 80's the past few times I've flown.
I will definitely fix the baffling and seals around cooler first. If that doesn't work I will move to a 4" sceet tube/fiberglass inlet to the cooler.
Should I just remove the cold weather door for now? It just seems like it is creating updraft into the cooler.
 
Similar issue

My Rv4 always runs about 180 to 200 on the hotest days. On a recent flight home from the midwest the temps suddenly started going up to about 215. I found that my tired old rubberized baffle seals were starting to fold down under airflow pressure and blocking the oil cooler hose opening.

Replace the seals. Temps back to normal


Cm
 
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