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Replacing cooling system fluid, 50/50


Rich

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Good evening,

 

Need some help here.

Rotax recommends replacing fluid after 2 years.

What is the best way to do so if your engine has the water jacket carb heaters?

Concern is air getting traped in the carb jackets.

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On the right side of the coolant radiator there is a low point hose for the system. Put a catch basin under it and pull the hose off. Then remove the cap on the expansion tank. If the cap is off to start you just get a bigger volume of coolant to deal with. Once it has drained then place a rag over the hose end and radiator opening and basin under it. They will be close together. Then I put my hand over the coolant expansion tank and blow down through about 4-5 times hard. This is an open system and  almost everything comes right out. Put the hose back on the radiator and re-fill. It takes about 2/3 of a gallon. This whole thing takes about 10-15 min.

 

Coolant is so easy to change and it takes so little there is no reason to go years past.

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Andy, Roger-Thanks for the replies.

 

How can I be certain that air won't be trapped at the carb water jackets or the expansion hose leading to the expansion tank?

Roger------I remember last year we spoke about the carb ice situation I had possible being caused by air trapped in the carb water jackets.

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Trapped air is possible, but not an overt problem. I have only once had to add any after I filled it and ran it for several minutes. After you fill it either run it for 5 minutes or go do a couple T & G's and come back and check it. This system isn't like our car and is fairly open top to bottom so air tends to rise to the top.

 

The carb water jacket system because it is so high up and small hoses is a little different.

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Roger,

 

All went well with the coolant change. There's a hex bleeder screw on top of each carb water jacket. A few things need to be taken apart to get to them.

I'm wondering if I didn't bleed at those points, would the air work itself out of the system.

 

I flew it for .4 hours to get it to operating temp, uncoweled and noticed that the right carb water jacket was much cooler than the left. I'm betting that there's air trapped there.

 

I replaced Exactly the amount of fluid that I drained using a quart size measuring picture

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Tom,

 

Thanks for the reply.

I made a phone call to Lockwood. Their opinion is it's not necessary to bleed at those points.

I also looked up the SI on replacing fluids. There is also a drain bolt with grommet that needs to be removed at the lower part of the water pump when draining.

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The water pump low drain point bolt is fine to use when draining. The problem is 90% of the people can't access it due to the firewall or hoses or other obstacles. When I do the drain as I described and blow down through the system and then do a hose change there is ony a scant amount fluid left, not to mention it's slower through the sall drain hole. There is Less fluid left in the system than when using the drain screw, but either works and just becomes one of those personal preferences.

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Roger,

 

Thanks again for your insite on the cooling system. I did blow down through the overflow bottle as suggested, and am sure that the system was empty.

That was a good tip.

 

Thank you for taking the time to make sure this was done correctly.

 

Rich

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