expansion bottle - overflow - 912s

[thermalator]

You are definitely getting boiling in the engine, this is BAD because a layer of steam will insulate the Cylinder head from the Water and heat transfer will drop, resulting in hotspots.

In my opinion 110 deg C is pretty high for CHT

Now Rotax seems to address this by changing their coolant recomendation in the last 3 years. They effectively say if your cooling system is such that you cannot keep CHT down, then you have to change to using Waterless "NGP+" coolant. Note this is NOT the same as 100% Glycol. This stuff has a boiling point over 400C. Problem is it is less efficient at thermal transfer, which means the Coolant temps are going to go up by about 15 C. However you never have to worry about boiling again and Rotax says you can now ignore coolant temps (even remove them) CHT is now all that counts.

Don't take my word for it - read the installation manual.

That said however, it is almost certain that you have an airflow problem thru your radiator, you need to check this by measuring the Differential air pressure across it using a Water manometer. This is a couple of meters of plastic tube forming a 50cm U tube in the cockpit filled with water One end is Mounted just in front of the rad like a pitot the other end - side on behind like a static. Anything less than 2 inches DP is bad.

I have seen some Bushbaby rads behind the exhaust box - looks ineffective to me

I fly a lambada motorglider equipped for aerotowing of heavy gliders in 40C Ambients. The rads are a bit ugly But I never see over 90C on coolant or CHT - normally sits around 80C, I have My oil cooler 30% taped (summer) to keep oil temp UP to 90C. SO I have an excess cooling problem.

[Frequent Flyer]

Hi Thermalator, i spent the whole of yetserday afternnon getting air out of the system! i also put on a different prop and adjusted the radiator so there is minimal gaps between the cowling and the radiator. send some pics of your radiators please?

[Carel]

Stephan,

How many cores in the radiator ?

[Ian]

(mixed to a ratio of 30%coolant and 70% distilled water

When I was on the 912 Maint course Niren said 50/50 mix, not 70/30.

Below is an excerpt from EAA USA sport mag (Phil Lockwood), send me your email and I will send you the article (there are 3 articles). I followed these instructions as I didn't want the extra 10 deg from the Evans coolant. I dont have a temp problem in my Savannah (at least not yet... )

Most probably saying the obvious but the bottom of the pipe in the bottle needs to be cut at an angle to work properly.

Cheers ian

[Morph]

yip, as soon as the one head gets to about 114/5 deg C it releases.

I have in the mean time closed up all the gaps around the radiator and it seems like the temps are a bit lower. But this is purely subjective

I will continue to test

In the meantime, if anyone has a spare 1.2 bar cap I will happily take if off you