PA-12 High oil temp

[txfirefighter628]

I have a PA-12 with an O-235C that I bought a few months ago that I'm having problems with high oil temps now. I have been flying in the mornings when the air temp is 65-70 and the oil temp was running 200-220. I had the prop repitched from 47 to 43 to make it a climb prop. This morning it was 235. I flew it a few evenings ago when it was 95 air temp and the oil temp redlined at 240. Could repitching the prop affect the cooling? I've read in previous post that 220-230 is not bad for these planes and I wouldn't mind if it stopped at that but I don't like it running at 240. I don't have a CHT or EGT gauge to check to see if the clyinders are getting to hot.

Also a local a&p suggested getting a stock spinner. He said the stock spinner will direct more air in to the engine, is this true?


Pic Of spinner I have now

There is a hole in the side of the muffler where it attaches to the cabin heat box. Is this supposed to be there? Would covering it up in the summer time help keep the heat from getting into the engine compartment?

 

[jcrowles]

I have a PA-20 with an 0-290 Lycoming that runs hot in warm weather even with an outside fresh air scoop. I have spent hundreds of dollars with different mechanics trying to cool it down. A Lycoming factory rep. told me its the nature of the beast. He said "Don't worry as long as you have a minimum of 40 pounds oil pressure. A larger oil cooler will help or fly at 10,000 Ft. and it will be in the proper temp. range.

 

[scruiser]

As far as the spinner is concerned, I doubt it would make a measureable difference. The hole in the cabin heat shroud is supposed to be there in order to dump cabin heat when unused. I would first ensure that the magneto timing is absolutely correctly set for that engine. If that is ok, make sure that the baffles and seals are in good shape and sealing as well as they can. Air that escapes the top side of the engine without going through the cylinder fins is not helping to cool the cylinders. Make sure the inner cylinder baffles are in place and directing air flow around the bottoms of each cylinder. I have read on the internet that with the "modern oils" that 240 is ok.....I would not like it either. Good luck.

 

[PerryB]

Does it have a vernatherm? If so, it would be my first suspect. I put a vernatherm in my O320 about 5 years ago and enjoyed the consistent oil temps. Then, about a year later the temp started going up. I installed a new Niagara cooler in place of the old Harrison (which is a nice weight saving upgrade and a better cooler) but saw little improvement. Finally pulled the v-therm and it was defective. I went back to the viscosity valve and just use various sized pieces of tape when the weather is cool/cold. Temps are back where they should be, around 100-105 above ambient with no tape.
I don't think the spinner would make more than a minor improvement. Maybe a few degrees.

 

[OLDCROWE]

Nice looking 12. Starting 3 weeks ago I'm at (BWD) once a month through next spring for a project in Early, any good Q to report that's in range of the airport's loaner Blazer?

Kirby

 

[txfirefighter628]

Nice looking 12. Starting 3 weeks ago I'm at (BWD) once a month through next spring for a project in Early, any good Q to report that's in range of the airport's loaner Blazer?

Kirby

Not sure what you mean by Q?

 

[txfirefighter628]

As far as the spinner is concerned, I doubt it would make a measureable difference. The hole in the cabin heat shroud is supposed to be there in order to dump cabin heat when unused. I would first ensure that the magneto timing is absolutely correctly set for that engine. If that is ok, make sure that the baffles and seals are in good shape and sealing as well as they can. Air that escapes the top side of the engine without going through the cylinder fins is not helping to cool the cylinders. Make sure the inner cylinder baffles are in place and directing air flow around the bottoms of each cylinder. I have read on the internet that with the "modern oils" that 240 is ok.....I would not like it either. Good luck.

Mag timing is good
baffles are good, filled any hole I could find with silicone
not sure on the inner cylinder baffles, will look in the morning

 

[txfirefighter628]

Does it have a vernatherm? If so, it would be my first suspect. I put a vernatherm in my O320 about 5 years ago and enjoyed the consistent oil temps. Then, about a year later the temp started going up. I installed a new Niagara cooler in place of the old Harrison (which is a nice weight saving upgrade and a better cooler) but saw little improvement. Finally pulled the v-therm and it was defective. I went back to the viscosity valve and just use various sized pieces of tape when the weather is cool/cold. Temps are back where they should be, around 100-105 above ambient with no tape.
I don't think the spinner would make more than a minor improvement. Maybe a few degrees.

Do do engines that do not have an external oil cooler have a vernatherm?
I do not have an external oil cooler.

 

[Gordon Misch]

Do do engines that do not have an external oil cooler have a vernatherm?
I do not have an external oil cooler.

If no oil cooler, no need for vernatherm. You should be able to see a basic cylindrical housing for your oil screen to confirm that.

 

[OLDCROWE]

Not sure what you mean by Q?

Sorry, BBQ

 

[PerryB]

Does the accessory case have oil cooler fittings that are simply plugged off? We had a Breezy years ago with a 235 that had a cooler so I think the engine is set up for one. If so, the solution seems clear, install a cooler. I can't imagime running in 90 plus degrees without one.

 

[Steve Pierce]

Ron, Do you have the seal between the air box and cowl? That makes a big difference on the Clipper with the O-235 and no oil cooler. I have a manometer you can borrow to see how much upper deck pressure you have. I have discovered the key is airflow. Tight baffles and you can add a longer cooling lip to help. Also the original temp gauges are not very accurate, some high, some low.

 

[skywagon8a]

...There is a hole in the side of the muffler where it attaches to the cabin heat box. Is this supposed to be there? Would covering it up in the summer time help keep the heat from getting into the engine compartment?
View attachment 20943

I'm not familiar with a PA-12 heat valve, but that does look a bit hokey. Where does the other end of that scat hose connect? The pivot for the valve does not appear to be in the correct location for proper operation. Is that the cabin or carburetor heat valve? Or what? There is supposed to be an opening to allow air flow through the muffler shroud under all heat valve positions. The picture seems to show that the heat is passing through that hole in all valve positions and that in the winter you will not be getting any heat in the cabin. You may indeed be getting surplus hot air dumped into the lower engine section. I don't see enough information in the picture to think otherwise.

 

[mike mcs repair]

too much oil in sump?? (don't ask how I learned that..)

 

[badmdcnman]

Flew my 12 with a 235 for the last 14 years in similar OAT with oil temp high about 215, normally 195-205. Your original 12 cabin air box appears normal and should not be contributing to your problem. There was no oil cooler with mine nor a vernatherm. If your baffling is OK I think I would look real hard at the gauge itself. Good luck. Let us know how you turnout.....Rod

Oddly enough with my recently installed 320 with oil cooler and Sutton exhaust I am struggling to get the oil temp above 140, and that is with a new gauge.....Rod

 

[txfirefighter628]

Scruiser - I do have the inner cylinder baffles

Gordon - I do have a vernatherm on my oil filter adapter. Took out the vernatherm and tested it, test good. Since I don't have an oil cooler do I just need to remove the vernatherm and plug the hole? Do I need a different oil filter adapter? I have an oil screen also, buts in the drain plug in the bottom of the oil pan.



I posted this with my IPad and sometimes it flips the pictures upside down, not sure why.


Oldcrow - a lot of people like underwoods but I don't care for it much. Smittys is hit and miss. The Sticks is what I consider the best in town but it's on the South side, about as far from the airport as you can get in Brownwood.

PerryB - No oil cooler fitting on the assc. case.

Steve - looks like there are a few gaps around the air box, I will seal them up. I would appreciate you letting me borrow your manometer. The oil pressure/temp gauge was overhauled in 2011. I know that doesn't mean it's accurate, will have to check it with a thermometer.



Skywagon - the other end goes to the bottom cowling, a fresh air inlet. The valve there is for cabin heat.




Mike - I keep it at 5qts, it holds 6 but spits outs the first one right away.

Thanks for for the help everybody.

 

[Gordon Misch]

Gordon - I do have a vernatherm on my oil filter adapter. Took out the vernatherm and tested it, test good. Since I don't have an oil cooler do I just need to remove the vernatherm and plug the hole? Do I need a different oil filter adapter? I have an oil screen also, buts in the drain plug in the bottom of the oil pan.

I'm sorry, I don't know the answers to those questions. I'm just a hobby guy, but some of the professional mechanics here will know. Or surely the manufacturer of your filter adapter would be able to advise you.

 

[skywagon8a]

.... Your original 12 cabin air box appears normal and should not be contributing to your problem.....Rod

Skywagon - the other end goes to the bottom cowling, a fresh air inlet. The valve there is for cabin heat.

View attachment 20957
View attachment 20958

Thanks for for the help everybody.

Hmmm? Barring any other solutions you could make a temporary bypass to that exit hole by rigging a hose to exit that air at the cowl outlet. Thus dumping that heated air overboard. That oil screen in the sump is to keep big pieces out of the oil pump. Your filter is a replacement for the factory fine oil screen.

Re-pitching the prop to a lower pitch thus providing a lower indicated airspeed at the same rpm could generate hotter temperatures due to less ram airflow. How much speed did you sacrifice by changing the prop pitch? You might try turning a higher rpm (within limits) for a higher airspeed. Have you noticed a temperature drop when in a slight dive to a higher speed? All things being equal, a higher airspeed will generate more cooling air and lower temperatures.

 

[irishfield]

Do you have the original screen housing around?? Put it back on and see what happens. I'm baffled as to why you would have a vernatherm when you have no oil cooler or ports for same to flow oil to when the vernatherm operates. I would only think that it is restricting the oil flow you have and causing it to increase the heat.

 

[txfirefighter628]

Gordon - I think the filter adapter is a stock lycoming part of a later model O-235? Not sure though

Skywagon - My cruise went from 95mph to 90 after the pitch change. I haven't climb high enough to try a dive to see if cools, but I'm sure it would. I thought cub drivers got nose bleeds over 500ft agl.

Irish - The plane was like this when I bought it, I don't have the original screen housing but could probley come up with one. The part were the vernatherm goes is where my oil filter screws on, so I would lose my oil filter if I took it off.

I think the oil temp gauge is working. It's about 100 in Texas today. This is just sitting in the hanger, plane hasn't been started in 2 days.

 

[PerryB]

Do you have the original screen housing around?? Put it back on and see what happens. I'm baffled as to why you would have a vernatherm when you have no oil cooler or ports for same to flow oil to when the vernatherm operates. I would only think that it is restricting the oil flow you have and causing it to increase the heat.

Same here. The vernatherm is useless with no cooler plumbing. Get rid of it and put a standard viscosity valve in and see what happens. You'll also need the plug that goes in place of the vernatherm. Just google Lycoming viscosity valve and you'll find just about everything you might want to know.

 

[don d]

Tried to sell oil cooler adapter for o235 in classifieds 6 months ago. Didn't have any interest so it went to the dump with some other junk.

 

[txfirefighter628]

So I worked on this all day and didn't fix a damn thing. Pulled out the vernatherm and tested it, tested good. Pulled off the oil filter base assembly and found it had some type of restrictor plate between it and the assc. case. Looked in the manual and found that this is supposed to be there. The drawing in the manual is a bit confusing, it looks like when using the oil filter base assembly you are not supposed to use a vernatherm and use a viscosity valve instead. My assc. case doesn't have a spot for a viscosity valve. My original set up is a oil filter base assembly with a vernatherm in the bottom, which the manual shows a plug is supposed to be where my vernatherm is installed. So I found a oil pressure screen housing in the shop and put it on with the vernatherm like the manual shows. Test flew, took off from 1400ft MSL and climbed to 4500ft at 600FPM at 60MPH, leveled off, set for cruise at 2450RPM and 90mph air speed, OAT at altitude was 80. Oil temp climbed to 240 after 10 minutes from take off. Dived at 110 MPH and 1500RPM down to 2200ft and oil temp only lowered to 230. Pulled out the vernatherm and installed another one that tested good, test flew again. Same results, oil temp up to 240 within a couple of minutes.

The drawing I have to go off.

My oil filter base assembly, the restrictor plate and a gasket

The oil pressure screen housing I put on, seems like it would let more oil pass though? There is a IO-360 in the shop that uses this same housing with a vernatherm but I'm pretty sure that engine would have an oil cooler when it's installed on a plane.

The manual says " do not use a spring and plunger(viscosity valve) on engines equipped with a vernatherm or engines with out oil cooler installation", so I guess I will put the oil filter base assembly back on and order the plug for where the vernatherm is and try it with out a Vernatherm, just looked up the price on the plug, $105. Gotta love the cost of airplane parts.

If that doesn't work next step is to borrow a friends wood prop off his PA-12 project and see if the prop repitch caused the problem, I wouldn't think that it would but I didn't have a problem until I had the prop repitched, so at least I will try it with a different prop and see if it helps.

 

[OLDCROWE]

What % power is 2450 at 4000ft on that engine?

Does it heat up if you don't work it so hard in cruise? Push it hard down low for awhile and my sc would heat up.

I know it's a different engine and aircraft but as I recall the manual for my 18-150 says the typical power for cruise is 2350 at 5000ft.

 

[txfirefighter628]

What % power is 2450 at 4000 on that engine?

Does it heat up if you don't work it so hard in cruise?

I know it's a different engine and aircraft but as I recall the manual for my 18-150 says the typical power for cruise is 2350 at 5000ft.

Redline is 2600RPM. I've tried cruising it at 2300RPM also, same result.

 

[txfirefighter628]

What the manual is telling you is the vernatherm vs. viscosity valve is an either /or thing. You can't use both. If you remove the vernatherm your engine is no longer "equipped" with it, a bit confusing at first but thats the meaning. My concern is not that the thing tests good or not, but when it gets hot and extends to seal off the sump return , its trying to send the oil down a path that doesn't exist in your engine. You don't have a cooler circuit.

So do I have to have one or the other? I don't have a place for a viscosity valve to go. So unless I don't need ether one I have to go with the vernatherm.

 

[skywagon8a]

....I know it's a different engine and aircraft but as I recall the manual for my 18-150 says the typical power for cruise is 2350 at 5000ft.

Bear in mind that your PA-18-150 manual power information is based on the original 74-56 prop being installed. Any other prop model/diameter/pitch combination would require a manifold pressure gauge in order to determine the power settings.

 

[OLDCROWE]

Bear in mind that your PA-18-150 manual power information is based on the original 74-56 prop being installed. Any other prop model/diameter/pitch combination would require a manifold pressure gauge in order to determine the power settings.

Very true, point was I think we often run our engines harder than we might believe and one undeniable is that and working harder = more heat that has to go somewhere.

 

[Steve Pierce]

The O-235 has a completely different oil system than something with an oil cooler. Take the Vernatherm out and either cut it off and use as a plug or buy a plug from whoever made your oil filter adapter. If you do not have that restricter plate installed the oil pressure will blow the filter.
Some good info on that here:
http://www.shortwingpipers.org/forum/showthread.php?7264-Oil-Filter-Adapter-on-the-O-235-C1
Does the PA12 originally have a blast tube on the oil temp probe? If so you might look at this:
http://www.shortwingpipers.org/forum/showthread.php?8851-0-235-Oil-Temp


I have a lot of time behind O-235s in the Texas summer. They run hot. I have also seen original oil temperature gauges vary from 10-30 degrees in the same airplane, engine and conditions. The tolerances are very wide. I would take the probe out and test it with a good candy thermometer.

 

[PerryB]

Sorry, I attempted to delete that last post before the world had the opportunity to witness my ignorance ! I didn't know the non-cooler engines had no vis. valve. As soon as I re-read your earlier post I scrambled back to delete my misinformation but alas, too late. I still think the vern. should be replaced with a plug.