What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Lyc. Oil Vernatherm working?

Mike_ExpressCT

Well Known Member
Well, we have finally finished the instillation of a new RV-10 oil cooler on our Lycoming IO-360-A3B6D, and it is being fed by a 4" SCAT tube running from the baffling behind the number 4 cylinder. On start up and taxi the other night we saw a continued climb in oil temps from 100 all the way to 230 after about 10 minutes of runnnig on the ground

Obviously, something is wrong, so we checked the oil cooler to make sure there were no air bubbles in the cooler, and then pulled the vernatherm for a boil test.

What we saw was that the element would not move until the water temperatue hit 180 degrees (two different thermometers were used), and by 195 it opened its full value. The element ended up moving a total of around 1/4".

Does anyone know what temp those things are supposed to open? It has 85C stamped on the top...is that when it begins to open or is that when it should be fully open? Also, how far is that element supposed to move? I'm guessing that it's a defective part, but before I go drop another $250 I just wanted to make sure.

Thanks guys! :)
 
Hi,

In my (limited experience of 2 Vernatherms!) 80-85C is when it starts, 95C is fully closed. 1/4" is about right, but difficult to know if it is closing the valve completely. Assuming all the other stuff (intercylinder baffles, RTV sealing, oil cooler hose routing etc have been done) would be worth trying to get a 'loaner' Vernatherm to try on your engine. The other option is to get a flow measurement device in the oil cooler look, but that is not something you are likely to have 'lying around'.

Carl
 
Well, we have finally finished the instillation of a new RV-10 oil cooler on our Lycoming IO-360-A3B6D, and it is being fed by a 4" SCAT tube running from the baffling behind the number 4 cylinder. On start up and taxi the other night we saw a continued climb in oil temps from 100 all the way to 230 after about 10 minutes of runnnig on the ground

Obviously, something is wrong, so we checked the oil cooler to make sure there were no air bubbles in the cooler, and then pulled the vernatherm for a boil test.

What we saw was that the element would not move until the water temperatue hit 180 degrees (two different thermometers were used), and by 195 it opened its full value. The element ended up moving a total of around 1/4".

Does anyone know what temp those things are supposed to open? It has 85C stamped on the top...is that when it begins to open or is that when it should be fully open? Also, how far is that element supposed to move? I'm guessing that it's a defective part, but before I go drop another $250 I just wanted to make sure.

Thanks guys! :)

The vernatherm (oil cooler by-pass valve) closes the port to the engine and forces all oil through the cooler when oil is hot (180-190F). Before that oil can flow through the cooler or back to the engine. Could be the device is not completely closing the engine port when oil is hot.

Another factor is air across the cooler on the ground. Chances are there is insufficient pressure in the cowl to force much air through the 4" duct to the cooler.

What was the OAT temperature when this occurred?
 
hummmm

and.......scat is not the best to use for cooling since scat has ridges inside the tubing. Others will disagree....oh well.
 
The vernatherm (oil cooler by-pass valve) closes the port to the engine and forces all oil through the cooler when oil is hot (180-190F). Before that oil can flow through the cooler or back to the engine. Could be the device is not completely closing the engine port when oil is hot.

Another factor is air across the cooler on the ground. Chances are there is insufficient pressure in the cowl to force much air through the 4" duct to the cooler.

What was the OAT temperature when this occurred?


Excellent point sir...there may have simply not been enough pressure to force air through the oil cooler. That presents a serious problem though, if I can't even taxi the airplane for 10 minutes before the oil redlines. We basically have the same "stock" setup as an RV-10 (except a smaller engine), and I haven't heard of them having many temp problems. You're quite possibly right though, but that will be an interesting challenge to overcome...

OAT was around 75 degrees that evening. Warm but not hot. Thank you for your help!
 
Thermostatic valve test photos

http://www.rvproject.com/20050409.html

My O-320 would have near redline oil temp when I had the oil cooler mounted on the firewall and a 3" SCAT tube to the rear of the #3 cylinder. Had Vapor Lock three times on the ground in the first 75 hours. Moving the cooler to the #4 Baffle fixed the high oil temp problem.
 
Another data point...

I have a firewall mounted cooler fed with 3" scat from above #4. I can taxi about a mile, do a runup, and take off in the summer and the oil doesn't reach 70C until around 1000' during the climb out. O360. Hmmm.

You verify the temp reading?
 
Which oil cooler ports are you using on the engine? You must use either the two that are located at the 11:00 position on the rear accessory housing or the center one and the 11:00 one that faces aft, not up. Does the oil cooler get hot when this happens? It really sounds like there is no oil flow through the cooler.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Another thing to consider...oil flow OUT of the engine should go into the bottom port of the oil cooler. Oil flow OUT of the oil cooler should come from the upper port of the oil cooler and be fed into the return port on the engine.

Of course, this implies that the two ports on the oil cooler are located one above the other in your choice of cooler mounting locations. This orientation and oil flow direction through the cooler ensures the oil spends a bit of time in the cooler and that the heat rejection process can take place. If the oil is allowed to "fall" through the cooler, then the cooler is not operating in an efficient manner.

If air flow through the cooler is a concern, then here is what I would try (I have not tried this, but I am looking for an excuse to purchase this item). Look for a Kestrel 4000 Weather Meter and the usb interface option that goes with it. This is a little hand held wind speed device and can be remotely connected. attach it to the back-side of the oil cooler and check how much air "flow" is coming out of the cooler. This could provide some relative measurements of air flow (and temperature) through the cooler.

Hope this helps.
 
I have a firewall mounted cooler fed with 3" scat from above #4. I can taxi about a mile, do a runup, and take off in the summer and the oil doesn't reach 70C until around 1000' during the climb out. O360. Hmmm.

You verify the temp reading?

My digital meter and probe was CALIBRATED before it ever flew. Checked it again AFTER having cooling problems.

Living in MN, you have MUCH cooler temperatures than we do in SoCAL. 100 F / 38 C is typical in the summer time. The Mojave desert is just over the hill. (actually mountain range) Death Valley is a little over one hour flight.

The 3" SCAT has a lot less area open for air (Pi * R^2 = 7 sq in) vrs 3 X 5 = 15 sq in. There is also FRICTION in the SCAT hose that will also reduce air flow. Makes a BIG difference in a hot environment.

Now with oil cooler behind #4 cylinder, pulling out of the hangar, taxi 1/4 mile, runup, and climb to 5,000 MSL (3,561 AGL) OT will be 180 F / 82 C when OAT is 100 F on the ground.
 
What oil cooler are you using, Gary?

The one Van's sells and recommends. EA OIL COOLER II

I now have 2,140 hobbs hours on the airplane. Only cooling problems I have had were with the cooler mounted on the firewall.

I do not recommend the cooler on the firewall behind #3 cylinder in HOT climates. Yes I know that it worked for some people in areas that are cool.
 
My oil cooler has been mounted on the firewall behind #3 cylinder for over 15 years (in Texas). I've not had any cooling problems. Hopped up O-320 with 9.5:1 compression.
 
I have an RV-7A with an 0-360 done by Barrett with 9:1 pistons. I have the cooler on the firewall with a 3" duct to it off of the number 4 rear cylinder baffle, and also put a flipper valve in the duct, controllable in the cockpit. I see max 212 degrees on climbout to 10K' in Atlanta on 90F+ days, and in cruise it will drop to 179-180. I usually pull the duct closed until I see 190-200. I had built my 6 this way as well, and it performed the same.
I did make one mad, and that was to duct the heater valve air down towards the exit after the valve, rather than just letting it run across the firewall and collide with the oil cooler air.
 
My digital meter and probe was CALIBRATED before it ever flew. Checked it again AFTER having cooling problems.

Living in MN, you have MUCH cooler temperatures than we do in SoCAL. 100 F / 38 C is typical in the summer time. The Mojave desert is just over the hill. (actually mountain range) Death Valley is a little over one hour flight.

The 3" SCAT has a lot less area open for air (Pi * R^2 = 7 sq in) vrs 3 X 5 = 15 sq in. There is also FRICTION in the SCAT hose that will also reduce air flow. Makes a BIG difference in a hot environment.

Now with oil cooler behind #4 cylinder, pulling out of the hangar, taxi 1/4 mile, runup, and climb to 5,000 MSL (3,561 AGL) OT will be 180 F / 82 C when OAT is 100 F on the ground.

Gary, of course average temps are cooler in MN, but I'm talking about 95F degree days which we get in the summer. And, we often also get inversions so that even at 7500' the temps are still quite warm. I don't have experience with OAT's above 95F.

It seems other variables are at play other than just scat/firewall/etc., since many with firewall mount, scat supplied do not have problems as significant as you experienced.

BTW, the question about temperature probe calibration was directed at the original poster Mike, as I don't believe that has been addressed yet in this thread.
 
BTW, the question about temperature probe calibration was directed at the original poster Mike, as I don't believe that has been addressed yet in this thread.


I appreciate it sir, and I think I have the answer I was hoping for. In short, I think my vernatherm is working fine, so my next steps will be to modify baffling as necessary for a better seal and also modify the lower cowling to give more area for exit air. I am planning on adding cooling louvers to the bottom of the cowl, as well as increase the area where the exhaust stacks exit the cowl. I would like to hope that, once the plane is airborne this won't be a problem as there should be sufficient positive air pressure on the top of the cylinders to push air through the oil cooler...the trick will simply be to keep the oil from redlining on the ground.

In any case, thank you for your kind help :)
 
Not so fast...

In short, I think my vernatherm is working fine, so my next steps will be to modify baffling as necessary for a better seal and also modify the lower cowling to give more area for exit air. I am planning on adding cooling louvers to the bottom of the cowl, as well as increase the area where the exhaust stacks exit the cowl. I would like to hope that, once the plane is airborne this won't be a problem as there should be sufficient positive air pressure on the top of the cylinders to push air through the oil cooler...the trick will simply be to keep the oil from redlining on the ground.

In any case, thank you for your kind help :)

Mike,
I have been working with RV's for a long time. My experience has shown, and that with the literally thousands of RV's flying using the standard cowl and baffles, with no modifications to the exit area, etc., any time someone makes a mod. such as you suggest, they are bypassing the root problem and fixing it (sometimes) with an unnecessary modification.

Personally I think you should get some help from an experienced RV guy in your area that could physically take a look at it.
None of us would except a doctors assessment of a serious illness over the phone...In the same vain, a cooling problem can't usually be solved texting to a few guys on the internet.

There is any number of things that could be causing your problem (it may even be a combination of a number of them) I suggest you investigate the true cause before you start making modifications.
 
Before you start on the bafffffelllls...........

Check the installation of the oil temp sensor. Make sure it is in the right hole!! There are two holes, one is about 1-2" deep and you should see oil, the other is about 6" deep and the temp sensor will see 220-240* seeing the backbone temp not the oil temp.:eek:

PS - you vernatherm.... is ok
 
My IO-360 a1b was running high oil temps. It was built with a 3" scat tube from the baffling aft of #4 cyl. to the oil cooler. Turns out, that was not near enuf airflow over the cooling fins. I ran another 3" scat tube from the front cowl cheek.....problem solved. I previously did all the vernatherm checking drill just as you have done.....same results, not the problem! Gene
 
Overheated Oil

RV-6 w LyCon IO-360EXP, 750 hrs SOH. Following a 30 min 7:00 AM flight into OSH last week my oil temp went nearly to 250 degs while taxiing to camping. Idle oil press dropped below 40 psi which is above lower limits but less than what I am accustomed to seeing. Spoke to Lycoming rep. Pulled oil screen per his advice and found no contamination. Did not check vernatherm due to circumstances. Replaced oil with fresh Aeroshell 15w50, flew 10.5 hours back home with no further incidence. Has anyone seen a similar problem? Perhaps the 90 kt arrival with a long taxi time was a factor? Oil cooler is mounted at aft left side of engine plenum. Thoughts, comments appreciated.
 
Following a 30 min 7:00 AM flight into OSH last week my oil temp went nearly to 250 degs while taxiing to camping....Perhaps the 90 kt arrival with a long taxi time was a factor?

Given that you saw no further problem in 10.5 hours, I wouldn't worry. The operating principle which extends a vernatherm makes it almost impossible to magically fix itself following a real failure.

Lemme guess, left turn off 27, long high power taxi in the bumpy grass, then circumnavigate the warbird area? You're not the first to get hot, and won't be the last. Common conversation in HBC.
 
Back
Top