Savannah – movement at last

I started servicing my Savannah weeks ago but it’s been ages since I’ve been able to do anything on it at all. As it has been some time since it has been flown and even longer since it was last serviced, I decided that I would give it a thorough inspection and service before taking to the air in it this year. It was during the engine inspection that I discovered a potentially serious problem with its cooling system.

The Savannah’s cooling system is much like that of a car. Its engine is water cooled with a radiator and when its engine heats up and the water expands the excess passes out through a tube in an expansion chamber at the system’s highest point into a bottle. Then, when the water cools down again, it is sucked back through the tube back into the main system.

I found that what had happened was that the metal outlet of the expansion chamber connecting it to the bottle had completely corroded away so the excess cooling liquid instead of flowing into the bottle was just being lost to the atmosphere. If it had been allowed to continue there was a real possibility that the engine would overheat leading, in the extreme case to a potential engine seizure and failure and it doesn’t bear thinking about if that was to happen mid-Channel on a flight back to the UK!

A replacement expansion chamber was called for and in preference to the original Rotax part that had corroded away and is very expensive, I decided to go for a less expensive Chinese made copy. I think it’s made from stainless steel, or maybe aluminium, so it will not corrode, and also looked to be extremely well made. I ordered it from Ebay and unfortunately it took several weeks to arrive, and even worse, when it did it wasn’t the correct part.

It turned out that there are two versions and I’d ordered the wrong one because I hadn’t checked before placing the order. The supplier was excellent when I let them know and offered to send the correct version without my returning the original, just for the cost of the postage. And they were true to their word, but unfortunately yet again the correct version took several weeks to arrive while the Savannah remained un-serviced and, of course, unflyable.

The part arrived a few days ago and today was the first day when I could get around to fitting it and doing the engine service. I started soon after lunch and when I’d finished the cooling system was back together and filled just with plain water so I could run the engine to heat and drain its oil, a new oil filter was fitted, new oil added and eight new spark plugs had been gapped and also installed.

And not before time. The old spark plugs still looked to be in excellent condition but they were due for a change and will be disposed of. The engine oil was also very black so it too was overdue for a change. And the best part after all this? I did the work in the shade inside the barn (which is why I didn’t start in the morning) and when I pulled the Savannah out again after I’d finished, it started instantly on the key and ran beautifully smoothly 🙂

The following pics show the new expansion chamber in place and the old one with its outlet tube totally corroded away.

Rotax recommend that the coolant system rubber hoses are replaced every five years and I was going to do that. However, I inspected all of the tubes very closely and they all seemed to me to be in very good condition, so I’ve reused them and their clips. What I have done, however, is order five litres of G12 antifreeze. I disposed of the old antifreeze when I drained the system to fit the new expansion chamber and as G12 is recommended for the Savannah’s engine, it is sensible to make the switch from the ‘bog standard’ ethylene glycol mixture that was in there. I’ll also do the same for my X-Air’s engine when I eventually get around to that 😉