Thermostats in Rotax Engines

[asra]

Some 582"s have a thermostat and some do not. In Gyro applications is a thermostat significant? I would appreciate some advice as I am setting up a replacement engine in a gyro which experienced a major engine failure. The new engine is fitted with a thermostat, the old one was not. What do you reckon?Birdmanpete.

[konvenetis]

The thermostat has 2 functions. 1. remain in the closed position when cold starting engine. this allows the engine to come up to operating temperature as quick as possible ( most engine wear happens when engine is started and operated cold. ) 2. restricts flow through the radiator

[birdy]

For starters, if the maker of the aircraft engine puts one init, then they obviously put it there for good reason, just as Kon said.But, if your wurried bout it stickn shut and boiling or cold shockn [ sticky one] the engine, then drill a small [ 3/16"] hole init. It will take slightly longer to warm up, but if it sticks, it wont boil, and wen closed, will still prevent the coolant getn too cold.Water cool engines run"n at optimum temps will last alot longer n one that is opperated without regulation.Just outa interest, wot was the "major engine failure"?

[asra]

Hi Birdy and Kon. Thanks for the input. I have always believed in the theory as expressed by Kon that the thermostat helps raise the temperature at start up and maintains the optimum temperature after that by regulating the flow rate but there is always the worry that it might fail in the full closed position. The suggestion of a 3/16" hole is really interesting. I have tested the thermostat and it is currently opening as expected in a cup of hot water. The engine that failed (in mid flight) pushed the number two conrod through the crankcase with damage to both halves. From a Gyro pilot"s point of view (mine at least) it seems terminal. No worries, I have some useful spare parts, carbies, coils, etc but its flying days are over. While I have been working on replacing it, I have wondered what led to its unexpected collapse. (Not a lot of hours according to the former two owners). The fuel did have oil in it. The radiator did have water and corrosion inhibitor. The 6mm bolt which retains the primary cog was loose but it is hard to see that as the cause of a seizure) Not too sure why there is such a bolt (except for assembly) as the cog itself is trapped and centred between the back of the gearbox and the block. So I am forced to think that the lack of a thermostat might be it.If I was to disassemble the wreck what else might I go looking for? Best wishesPeter

[asra]

I made a silly mistake in my reply to Birdy"s question. The primary cog is sandwiched between the faces of the gearbox and that 6mm bolt attaching the cog to the doughnut should prevents wear on the gearbox case faces. Apologies. Peter

[asra]

It was a pre blue head model? Are there any precautions which apply to that type. ie more oil etc etc?Peter

[asra]

There is a similar thread running on the

[Adrian S]

Pete,It is my understanding that ROTAX installed thermostats on the 582s to combat cold seizures that occur after a prolonged descent at idle. Practice Autos fall right into that situation!My stong advice would be to follow Birdys advice - ROTAX are seldom wrong especialy in an engine with the long history(more than 10 years in operation across the world).On another matter I still havent recieved the CD re Wongan Hills?Just my 10c,ThanksAdrian S

[asra]

My thanks to all of you who offered suggestions. In continuing with this project I have discovered another useful detail, The 582 block has two coolant by pass plugs. In the old (wrecked) motor both were plugged. In the "new" motor, the upper one (upright installation) was fitted with a nipple. In the manual this nipple is connected via a hose to another nipple fitted into the return pipe, at the high end of the hose to the upper tank of the radiator. In a way this is a "big" version of Birdy"s 3/16 hole in the thermostat. It certainly must increase the flow rate across the whole range of operations. The manual goes on to show the flow rate as being between 65 to 70 litres per minute at 6,500 rpm. Pretty awe inspiring. In my system the main hoses feature at least two constrictions of about 18mm, which really cannot be helping. Incidentally the manual also shows the radiator cap as being 0.9 bar. Once again the old engine was out of step with Rotax, using a 1.2 bar cap. Thanks for your input. Testing thrust this weekend.Birdmanpete

[bones]

Pete,The hose going up to the header tanks primary job as i understand it is to allow any air out of the system, well that was my understanding of it from many moons ago.

[birdy]

Recon Bones is rite [ my memory aint real flash either].If theres only one line, its only an air bleeder.If its a bypass, theres bota be a compleated circit. one out and one back.

[asra]

For what its worth fellas, I run my 582 gray head without a thermostat, and have 80+ hours on it now.I use a double folded paper towel across the Volkswagen Rabbit radiator during my "warm-up" before flight.It takes about 2 minutes to reach 140 degrees. In flight, on a 90 degree day, my coolant temp stays solid on 150 degrees, regardless of climb, descent, hover or whatever. I flew the other day in 47 degree temps,and she stayed right at 140. As far as the nipples in the top of the cylinder head, I plumbed the one on the mag end of the engine back to the coolant reservoir, per Rotax. I believe it is a steam vent. I have the overflow nipple on thecoolant reservoir plumbed to a small tank about the size of a pack of cigs. This tank is mounted 5 inches higher than the engine. In 80 hours of operation, I have checked the coolant level before every flight, and have not lost a drop.