Question for our engines expert: I have an RV-6 with a Lycoming O-360 and in winter, even with the louvres of the oil cooler closed, my oil temperature may only reach about 150°-160°. Can I install a shut-off valve to prevent oil flow through the cooler in cold weather or does oil need to flow through it to keep oil pressure from getting too high?
Paul Steger
Answer: Paul, the issue you mentioned is not an unusual occurrence during the cold weather and there are remedies.
Several of the major airframe manufacturers used to provide a winterization kit for several models of aircraft. This kit was typically just a piece of aluminum that was placed over the oil cooler.
I don’t remember the specifics of how this was mounted, but there is also another method used that I’ve heard about: Some folks use a strip of “100 mph” tape — also known as duct tape — across the oil cooler.
You may want to try this beginning with one strip about 2 inches wide and then fly the aircraft to see if there is any noticeable increase in your oil temperature. If little or no increase is indicated, then I’d add an additional strip to see if that provides any help. Remember, if a little bit is good, a whole lot more may not be better!
I hesitate to tell you to block the entire cooler off because I don’t want the oil temperature to exceed the maximum of 245°F.
It may be worth your time to verify the accuracy of your oil temperature gauge before making any modifications.
While this answer may be just a bit late for the remaining cold temperatures we have left in 2022, it is something people can put in their files for future referral.
ANY mechanical device inserted in a system that has a well established/simple flow path adds a failure mode for: [a] the Valving; [b] each added fitting and hose/tubing segment added to a system becomes another maintenance/inspection requirement; and [c] become a potential leak-source [which could in increase the smoke/fire hazard]; [d] etc.
Here is the Lycoming ‘ Understanding Oil Flow ‘ tips letter;
https://www.lycoming.com/content/understanding-oil-flow
It lists all the different variations on the accessory cases wrt, oil cooler, oil filter, pressure bypass valve vs thermostatic valve.
So, the question to ask is what accessory case is on this O-360 , and what is connected to it ?
Not the expert but reviewing Lycoming oil flow schematics show the cooler on the pump discharge, pressure, side and parallel to a cooler bypass valve. Having a Warrior II, a C-172, and a M20C.with Lycomings in Colorado I never installed a winterization plate, though may be useful in far northern latitudes . Perhaps partially blocked bypass valves could be a problem by passing excessive oil though the cooler.
Note that certified aircraft have a specified oil cooler, if they are equipped, or as an option.
The RV may have been built with an overly large cooler.
Aircraft Spruce lists 16 oil coolers, from 7 row, used on a lot of certified aircraft, to 16 row, used on high horsepower and turbine aircraft.
The article does not list what oil cooler is installed.
BTW, my Cessna 175B has a 10 row cooler, which is way oversized. Even in the summer here in northern California I have to cover 1/3 of the cooler to keep the oil temp at 160-180 degF. Otherwise it will be about 110 degF…!
In the headline of the question he asks “can I bypass the oil cooler?”. But in the text of the question he asks “can I install a shut-off valve?”. The answer to the first is “yes”, that would just make it act like an engine that does not have an oil cooler at all. The answer to the second question is “absolutely not”, as that would interrupt the normal oil circulation to the engine and cause fatal damage in a very short time.
The question was – “Can I install a shut-off valve to prevent oil flow through the cooler in cold weather or does oil need to flow through it to keep oil pressure from getting too high?”
No one has answered that question, also note he said he has already covered the oil cooler.
I believe the answer to his question is Yes you could install a bypass valve.
And no, it will not affect the oil pressure, as that is what the oil pressure regulator does.
William,
The oil cooler is an option on the Lyc, O-360 series, and there are 2 configurations.
ref lyc Operator manual 60297, [ available as a pdf online ].
Both have the oil temp sensor on the oil return fitting. So, bypassing the cooler may not provide accurate oil temps…..lower than actual.
One of the optional setups includes a thermostatic temp control valve, which should provide some oil temp control.
There is no mention in the manual on the size of the oil cooler, so your cooler may be too large.
I fly a Continental engine with an oil cooler and vernatherm temp control valve. I’ve found that it does not control the oil temp, not bypassing the oil . So my oil temps were very low, 109 degF. So, I had to tape off at least 1/2 the oil cooler in 60-70 degF temps t get the oil up to 160-180 deg.
BTW, Lyc advises to not run the oil below 140 degF, 160-180 deg recommended.
Using tape is an easier and more reliable setup…fewer connections to leak.
another answer;…. ‘Can I install a shut-off valve…’ Absolutley NO.!
All the oil flows from the oil pump, through the cooler , [ or thermo bypass ], and to the engine.
Installing a shutoff valve will block all oil flow to the engine, and the engine will self-destruct shortly…!
I’ve used “no residue” duct tape on my RV-9A IO-320 to cover my oil cooler for years. As others have said, it works fine except when there are big swings in air temps locally or on cross country flights. I finally got tired of adjusting the amount of tape and removing the cowling and installed the louvers from Vans with a cable into the cockpit. On a recent flight with an OAT of 20F the oil temp settled at 175 deg. It will be nice not dealing with the tape anymore.
Be sure that bypassing the oil cooler does not also bypass the oil pressure pick-up point.
I installed oil cooler shutters directly on the inlet side of the oil cooler. They are simply small aluminum jalousie windowpanes that are adjustable through a push-pull control in the cockpit. Here in NW Arkansas, it is not unusual to depart in 10-degree (F) weather and land 2 hours later in 60-degree weather, so I had to have something adjustable. When the shutters are fully closed, they block almost 100% of the airflow.
If this wouldn’t provide enough temp control, then could the problem be too much airflow across the oil sump cooling it more than anticipated?
I should clarify – 2-hours later and 300 miles southwest.
Can you explain in better detail when using the aluninum foil, can you explain how to cover the oil cooler ( inside or outside or both).
Cessna lists a ‘winterization kit’ that covers the upper 1/2 of the oil cooler.
Most oil coolers have the inlet and outlet on one side, with a header tank that moves the oil from the lower half , to the upper half.
I agree that using aluminum foil tape is best.
Start by covering part of the outlet half, usually the upper half of the cooler.
I note how many sets of fins to cover vs oat. I made a chart to indicate how many of the 10 sets of fins to cover on my cooler.
Access is easy for me since the GO-300 has the oil cooler up front, next to #5 cylinder.
To answer your question on where to put the tape;
It should be put on the air inlet side, where the higher pressure will better hold the tape to the cooler.
Place it over a number of rows of fins, and tubes ] , to block the air flow to those parts of the cooler.
You can use small strips to cover a few sets of fins across the cooler.
Then it’s easier to add or remove the tape from a few rows of fins at a time, to adjust the oil temp.
I had the same issue on my RV-6 and used the Aluminum Foil tape as Steve & Jim did. It is readily available and does the trick without leaving any residue when removed or repositioned.
I started by covering half the fins of the cooler and went from there. After testing and adding more tape, I ended up with about 90% of the fins covered…
I do what Steve Rush does and use the aluminum foil tape. It won’t melt and it doesn’t leave any adhesive residue on the coil of the cooler. It’s quite easy to use with no clean up when you remove it.
I have the same issue in my IO-360 RV-8 and also had the issue in my O-320 RV-4. I use aluminum foil tape to block off the front of the cooler. Living in the Pacific Northwest, on the wet side of the mountains, I don’t fly in a lot of hot weather. I leave about 1/3 of the cooler covered all year. As fall sets in I cover a little more and by about December I have the whole thing covered.
With OAT’s in the 20s and 30s I can keep the oil at 180 degrees. With an OAT of less then about 20 I can’t maintain 180 and it will go down from there.
Once spring arrives, I reverse the process and remove the tape slowly. The only drawback to this process is the weird weather we have been having the past couple of years. Once in a while we get a strong thermal inversion with temps on the ground in the 30s and 40s, but in the 50s at altitude. In that case, my oil will run a bit “hot”, by which I mean between 195 and 200 degrees. While that temperature isn’t bad for it, it is higher than I like to see.
A good option is a moveable shutter mounted in front of the oil cooler. This allows for easy adjustment without removing the top cowl. A control could even be run into the cockpit for control on the fly. Anti Splat Aero sells a shutter that would work.
On my RV-4 I also though about bypassing the oil cooler. I was thinking of interconnecting the inlet hose directly to the outlet hose, thereby taking the cooler completely out of the circuit. I’m pretty sure that I could have gotten away with it, but I was never brave enough to try.
RVs tend to be over cooled in all but the hottest of climates. Posting the same question to Vans Airforce dot net will provide a wealth of information, or better yet, use the search function to read what has already been posted.
Over cooling is a much better problem to work with than under cooling.