Slow decrease in coolant level

[WingedFrog]

I am curious to know if anyone experienced this in the first hours of Rotax operation. I am at 20 hours on Hobbs and since the beginning I noticed a slow decrease of the level of coolant in the expansion vase (about 1" over the 20 hours). Today I removed both cowls and could not find any sign of leak on any pipe used by the cooling system. I tightened all clamps involved and will continue to monitor. My Rotax man told me that it's normal to have a decrease in the first hours as bubbles are pushed out of the circuit but 20 hours seem a bit long for this to take place.

 

[RFSchaller]

I didn't lose any coolant, but I it wouldn't concern me unless it continues since it's easy to see how air gets trapped during the initial fill.

 

[rvbuilder2002]

It is very difficult to fill the system and not still have some amount of air present.
Pushing the tail down as low as possible with the cap removed from the expansion tank seems to help some but is no guarantee.

Keep watching the level. If it remains stable from this point on, my guess is that you have been clearing out trapped air.

 

[roger lee]

Hi Wingedfrog,

On a new plane as they said in the other post some air my be working itself out of the system. If this does continue then check these two areas. One you are well aware of and that's just tightening any screw clamps and checking the spring clamps. If a spring clamp is too far back towards the end of the hose verses up near the bead on the metal tube the hose can weep.
The other place that gets over looked all the time is the 90 degree coolant elbows on top of each cylinder. They may not be loose to the touch, but if the seal on the threads are broken they will weep. The reason you can't usually find a lot of coolant at either location is the fast moving air flow through the cowl that sweeps the fluid away and makes your weeping area look clean. Look around the base of the 90 degree coolant elbows for tattle tale signs of coolant. Look close around the edge where it screws in and you may see a very slight discoloration of coolant. You can double check the hoses by squeezing from behind the spring clamp and milking the hose towards the open end and look for that tattle tale drop of coolant.
The elbows if oozing can be removed from the plane.Remove the elbow flange. The elbow needs to be heated well to unscrew the elbow from the flange it screws into. Clean the threads on the elbow and flange well with Lacquer thinner. You can use either Loctite 243 blue or 648 green. I prefer the 648 because it never leaks again and won't come loose from being bumped. When you apply the Loctite put it on both sets of threads and re-assemble and put it back on the engine to check alignment. I usually mark it with a magic marker before I pull it off to retain the alignment I want. Do not disturb it for 24 hours or at least over night before adding the coolant back.

 

[funflying]

Thanks

Roger,
Thanks for your detailed posts and sharing your knowledge about maintaining these Rotax engines. I am planning on going to a Rotax class to learn more about regular maintenance and good operating practices. Ant suggests?

 

[WingedFrog]

I will support Patrick in big kudos for Roger, who knows his stuff and shares it selflessly.

 

[crashley]

coolant leak

I will support Patrick in big kudos for Roger, who knows his stuff and shares it selflessly.

I had a small coolant leak when I first filled the system the only evidence of the leak was a small amount of a white crystal / powder left on the head near where the hose connects this residue is left after the coolant evaporates and is a lot easier to find than trying to find an actual coolant leak

 

[roger lee]

Hi Crashley,

I agree some coolant leaks are hard to find sometimes and it takes a sharp eye to find trace evidence. The white crystal you mention is one of those trace indicators. Once in a while an oil leak can be tough too because the air flow through the cowl blows it off the leaking part and keeps it clean, but the oil is now back some where else and it fools you into suspecting the wrong part leak. I have certainly been fooled a time or two.