Having just calibrated the oil tempterture indicators in my C152’s tha anecdotal evidence from the pilots is that the temprerture of the oil is not reaching the Lycoming recomended level of 180F.
This comes as a bit of a surprise in the middle of the summer when the aircraft is flying circuits and using lots of power and does not bode well for the oil temperiture when operating in mid winter.
Any one else in EuroGA land having the same sort of problems?
I don’t think that with your knowledge you need my advice but I would think that something is wrong with the instrument.
The only way to find out is by using an external gauge to measure the oil temp. Otherwise, try another probe to the current gauge and if the same reading then another gauge. Did you check the wire for resistance?
When I say the indicator was calibrated I put the Temp probe while still conected to the aircraft in a can of oil and heated it to 180 F ( this was checked with a reliable thermometer ).
180F was marked on the indicator, the top and bottom of the range also being checked.
Today with a ground Temperature of 20C+ I an being told the oil Temp did not reach 180F during flight.
I have now put in place a pilot survey to try to check oil Temp vs OAT in normal service.
The low oil temperiture may well be the sorce of some corrosion problems that Lycoming engines suffer in some aircraft instalations.
We leased in a C152 while one of our C150 had its engine overhauled. The oil temperature gauge only just gets into the green. The probe was checked and changed and both were ok.
In the warmer weather we have been getting higher oil temperatures but engineering still think it runs too cool but don’t know why.
What I do know is it currently suffering badly from lead fouling of the plugs.
The lead fowling fowling I can help you with, the lycoming shut down drill is :-
Set 1200 RPM and do most of the normal shutdown checks.
set 1600-1800 RPM & maintain for 20 seconds.
bring the RPM back to 1200 then instantly bring the mixture to idle cut off.
This has stopped plug fowling that was a big problem that resulted from long slow taxing after landing.
Aparently there is a chemical in AVGAS that helps the lead vaporise, this chemical only starts to work with the heat produced at 1600 RPM.
Having talked to a lot of people in the Technical departments og both Lycoming and Cessna there is a lot of uming and aaaring when you mention the oil Temp issue with no one wanting to be quoted about the reasons for this, no doubt for fear of a masssive court case.
What is starting to become more clear is that the O-235 installed in a C152 is not a happy engine if operated in a northern european climate, corrosion issues abound in aircraft that get less that about 300 hours a years in the air.
one has to fill in the missing bits of the jigsaw from what the company repps dont say but it would seem that the C152 has a massive over cooling problem when operated in the northern european climate ( even in the summer ) and this particularly in the winter results in the corrosive eliments from combustion not evaporating and much corrosion is the result.
this problem is not seen in the PA38 or DR400 fitted with this engine.
I was rather hoping to find some one who was having the same problems and who had independently come to the same conclusion.
At the monent I am running an operational monitoring of OAT vs oil temp in my C152’s to prove my theory, once I have the data I will make my next move.
Why don’t you put duct tape on the oil cooler?
Duct tape on the oil cooler has been considered but as the oil is only directed to the oil cooler when with a view to keeping the Temp at 180 F this would seem unlikely to have any major effect.
The most likely course of action would be to fit the Cessna winterization kit to the engine cowls, this will cut down the cooling airflow to the engine, this kit also has an oil cooler blank but I think this is likely to be going to far in the summer and as a first step I intend to leave the oil cooler unrestricted and let the thermostat to regulate the oil temp.
There is also some hint that the cylinders running too cool is part of the cylinder bore ridging problem that is largly dure to the corrosive eliments that are not evaporated by an oil temp that is too cool.
A_and_C wrote:
There is also some hint that the cylinders running too cool is part of the cylinder bore ridging problem that is largly dure to the corrosive eliments that are not evaporated by an oil temp that is too cool.
With all due respect A&C, where do you get this stuff ?
A small step at the top of the bore is perfectly normal since the top piston ring does not reach the last 1/8" or so. Then there is the junction of the barrel-head which does collect a bit of “junk” , including oxidation.
But never heard of “bore ridging problem(s)” , since all this is perfectly normal 
It is not at the top of the bore, it is at piston ring BDC, this ridge then gets so large that the piston pin plug gets “bacon sliced” and you find most of it in the oil filter as small aluninium chips.
This is why the Lycoming warranty on O-235 cylinders is half that of any other cylinders, most of the O-235,s are in C152 aircraft hence the warranty time reduction due to the large number of claims.
The monitoring of the oil temp is producing some interesting results, it would seem that even in the hight of the English summer during a typical training flight the oil Temp is not making the Lycoming recomended 180F, if this proves to be the case across two or three weeks of operation with a large number of pilots then it will be clear that there is an overcooling problem in normal operation.
The two most likely results of overcooling are corrosion because the water resulting from combustion is not evaporated and the bore not running the correct clearance, Lycoming put a choke in the bore to allow for expantion due to Temp variation between the head and the base of the bore but it follows that if the bore is running over cool the piston (& ring) clearances will not be at optimum. my personal feeling is that the corrosion is the biggest issue.
The oil temp system has been calibrated using the Lycoming recomended procedure so I have a very accurate 180 F bench mark, all that I am now waiting for is to gather the data from two or three weeks flying.
Thanks for the leaning advice – of course the main problem. Is people don’t do what they are told.
The company we get our c152 from have a total of 4 that they lease out. They feel that they all run cool and had considered putting on winterisation kits.
In the last 2 years two of there aircraft engines have had to be rebuilt but that was due camshaft failure and was thought to be second dary to corrosion due lack of use with the downturn in the economy.
I pray for the day someone comes out with a decent airframe matched to a rotax engine.
