water radiater hoses

by Ken Ryan in 912 / 914 Technical Questions 7 years ago

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Re: water radiater hoses

by Bill Hertzel » 7 years ago

Bill Hertzel

13 1.95k 7.97k

Ken, I feel your pain,

During operation, the Radiator does not care which way the coolant flow, Up or Down is OK.
The coolant passes through the radiator at Fire Hose Speeds and will flush any air bubbles in the system with it.
The important thing is that the expansion tank is at the high point of the system.
When the coolant system is new, it will have a small number of trapped air pockets.
It will also have dissolved air in the water portion of the coolant.
You can see these bubbles appear in a pan of water as it approaches a boil.

After a few Heat/cool cycles of the coolant, the water will become de-aerated
The radiator cap has a small valve that opens to vent the air and to allow coolant from the overflow bottle to be sucked into the radiator each time it cools.
Eventually, the coolant system become 100% filled with coolant with no air whatsoever.

I said all that to explain this...

If your radiator has both ports on the same level it makes no difference.
If your radiator has one port above the other, when the engine stops, any air in the coolant in the radiator is going to rise to the top.

If the upper radiator hose is attached to the water pump and assuming the water pump is above the radiator,
The air bubble is going to have to pass through the water pump and the all the cylinder plumbing to reach the expansion tank. This may never happen.
If the Radiator is above the Water pump, the air will remain trapped in the radiator.

If the upper hose is attached to the expansion tank, the air will have an easy path to the expansion tank and out of the system.

So YES, it makes a difference!
The UPPER-MOST Radiator Hose should be attached to the expansion tank to make the elimination of the air from the system most efficient when the engine is stopped.

Will it work the other way around? Probably!
It will just take much longer to clear all the air.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

Thank you said by: Ken Ryan

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Re: water radiater hoses

by Ken Ryan » 7 years ago

Ken Ryan

28 360 928

Thanks everybody. Bill, your explanation of the theory makes sense. I'm going to count on the fact that there are a lot of SuperSTOLS and Highlanders with 914s so I will do it their way. I do wish they had followed the manual, though.

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Re: water radiater hoses

by James Murray » 6 years ago

James Murray

0 1 0

Can't find an exact answer but I have a buyer for my 701 that claims all rotax engines have to have ALL the rubber parts, hoses etc replace every 5 years? and the engine would have to be pulled from the plane??

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Re: water radiater hoses

by Roger Lee » 6 years ago

Roger Lee

126 5.14k 4.61k

Rotax does want all the rubber inside the engine compartment changed every 5 years. This isn't limited to just hoses. Most engines can be left on their mounts in the engine compartment. Once in a while a really short nosed plane like the Flight Design needs to have an engine pulled to get to hoses and rubber engine mounts behind the engine.
This recommendation is in the Line Maint. manual in section 2

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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