Rotax 532, 582 exhaust, radiators, thermostats
Rotax 532 - 582 Exhaust system
While the early two piece exhaust systems used on the Rotax engine proved to have several problems, notably cracking down the elbows, and baffles breaking loose, the new three piece exhaust is literally trouble free.
However some manufacturers in order to fit the exhaust into their cowls have welded the 90 degree elbow onto the Y pipe, or have shortened or lengthened the exhaust tuning length. This can cause failure of the muffler, loss of power, and or engine overheating and seizure.
USE the three piece exhaust as it is supplied by Rotax for best performance and reliability. When installing the exhaust make sure it rubber mounted and that the system is allowed movement. Make sure all springs and snug and that they are pulling straight, and not at an angle. After the springs have been installed properly are under the right tension, and safety wired FILL the spring with silicone. This will stop harmonic vibration and if the spring does fail the spring pieces remain in the silicone not in your prop.
On the 532/582 exhaust manifold only three bolts are used on each side to secure the manifold, while many owners have installed studs, cut down bolts etc. to fill the fourth hole it is not necessary.
If you are installing an exhaust gas temperature gauge into the Y pipe the probes must be 100 mm from the face of the piston, and in the center of the pipe. You should be using a gauge and probe for each cylinder if you intend to monitor your engine correctly.
The latest Y pipes coming from Rotax have fittings already machined into the manifold for proper placement of the probe.
Rotax Radiator Cooling System
Probably the most problematic part of a Rotax 532/582 engine installation is the liquid cooling system. Why? Because of the varied application of the engine. Some engines run in cowls, other in open air, in some cases the radiator is found six or seven feet from the engine.
While all of these can contribute to problems with the engine, in the form of overheating, if certain things are done properly you can just about get away with anything when mounting a cooling system. One of the first things is to have a system that allows a flow rate of fourteen gallons per minute. This simply means that if water were poured from a container into one end of the rad - fourteen gallons of fluid should go through the rad in a minute.
The next is to have someway of adjusting the AIR FLOW going through the radiator. This can be in the form of a set of louvers, or just a mechanism that adjusts the rad up and down in the airflow, The purpose of this is to maintain a constant temperature in the cooling system -especially during the change of seasons. The temperatures you are looking for are 140 degrees Fahrenheit to 180 degrees, with 160 degrees being the preferred temperature.
Many aircraft I have seen in the field exceed the 180 degree F temperature, This is not the fault of the engine it is the fault of the designer.
Install a ROTAX 532 - 582 thermostat.
Other things you should remember are :
Use a water temperature gauge that uses a probe that comes off the top of the cylinder head, there is a threaded hole for the probe for this purpose. I have seen some manufacturers use car water temperature gauges and have the probe come off a "T" in the line. The difference between the two locations and types of probes can be in excess of 50 degrees difference.
When mixing your anti-freeze to water solution use only DISTILLED WATER! Some owners have used well water, water from a tap with a water softener, etc. The block and cylinder head used by Rotax are ALUMINUM, as soon as any other metal comes in contact with it the aluminum will start to corrode. In two cases where owners have sent me engines with overheating problems, I have had to throw the cylinder heads away because there was so much corrosion in them that the water would not flow through!
Install a ROTAX thermostat. A thermostat brings the engine up to operating temperature quicker, and helps maintain it during long taxiing or long slow approaches. In my mind a thermostat should be something that every 582 should have.
It is also an item that should be visually checked every four or five months. Over the years I have seen about a dozen of them that have failed at solder joints, or have stopped working.