I should be careful what you pray for, the Rotax is not without its issues !
As you say low flying hours make the problems much worse but I have the same sort of hours per year on my PA28 but without the corrosion issues, This is why I think it is a Cessna/O235 issue as the PA38 @ DR400 with this engine dont have the issues.
Cruising around the net, I find mention of two different types of Lycoming OEM oil cooler flow control, thermostatic and spring/viscosity based. Has whichever of those applies to a 152 been checked and found fully functional?
A_and_C wrote:
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.
1 – I seriously doubt that there is much correlation between your oil temp and your cylinder head temps.
2 – Lycoming did not invent cylinder taper and just about every single piston engine has it since before you or I were born.
3 – If you’re serious about this then full CHT probes and a gauge should be installed.
Silvaire
One has been is OK the other will be checked thhis week but as both aircraft perform exactly the same I doubt anything will be wrong with the thermostat.
Michael
1- I dont think I said that, in my opinion the whole engine is overcooled for the northern european environment.
2-I dont think that I said anything other than the engine had a choked bore and that if the cooling was not correct the clearance between the bore & piston would not be correct.
3-While a full CHT gauge setup initaly sounds like a good idea the large amounts of water found in the rocker box on shutdown and the total lack of the type of carbonization around the hotter areas ( that you see on other Lycomings) all suggests the whole engine is getting too much cooling air. As one way of reducing the cooling air would be fitting an already approved kit for reducing the cooling airflow it would seem to be a good place to start.
On my Cessna 180 (O-470) there’s a little right-angled pipe that sits in the front of the cowling which blows cool air over the the oil-temp sender to correct the temperature reading; it was added to overcome the pilots ‘anxiety’.
What are the EGTs saying? Do you have a gauge for that?
What type of oil are you running?
A_and_C wrote:
3-While a full CHT gauge setup initaly sounds like a good idea the large amounts of water found in the rocker box on shutdown and the total lack of the type of carbonization around the hotter areas ( that you see on other Lycomings) all suggests the whole engine is getting too much cooling air. As one way of reducing the cooling air would be fitting an already approved kit for reducing the cooling airflow it would seem to be a good place to start.
Given the choice between over heating cylinders and dealing with abit of post-flight condensation, I’ll take the latter, every time.
Michael
I’m not going to change anything without enough evidence to be sure it is safe, the trouble with pilots is that if you don’t give them enough guidance they tend to make things up and their opinions go with the crowd.
Over tha last week or so we have been running a monitoring form to check OAT vs Oil temperiture and flight time, the questions on the form are designed to be simple and unlikely to be misinterpreted, at the moment it is clear that the oil temp is going well above the 180F point, this flys in the face of what pilots have been telling me in the past.
Of course this is in the middle of the summer when the OAT is around the 22 C mark, some night flying training is going on so the results from the lower temperatures at night might provide a bit more insight into the overcooling issues but it would seem that this is not a summer issue however when doing night training in the winter I have seen the OAT on the ground at -12 C and at 4000ft below -20 C, my guess is that these sorts of temperatures have a big impact on oil temp.
The current research is intended to find the point at which the OAT no longer lets the engine maintain an oil temp above 180 F and to manage the cooling air to the engine so +180 F oil temp is maintained for as much of the flight as posable during normal operations.
This along with more regular oil changes during winter flying should help to keep the corrosion problems to a minimum.
