Coolant bottle fittings?

Bad terminology on my part, Sean. Yes, a small hole drilled in the cap is enough to vent the overflow bottle, I was thinking more about getting the line into the overflow bottle from the expansion tank. 

Hi Steve,

 " I was thinking more about getting the line into the overflow bottle from the expansion tank. "

No additional fittings required;

Drill a second hole in the cap, just large enough for a snug fit on the tube. Extend tube to bottom of overflow bottle/reservoir. This will give you a single tube (no additional fittings) from so called expansion tank to reservoir.

The function of the reservoir to to allow hot expanded coolant in the cooling system, to enter and then, when system cooling, be drawn back into the cooling system.

Of course you can achieve this by adding a fitting, to the bottom or to the cap of the overflow reservoir , however this adds to cost & complexity. The complexity is two additional (to what I have suggested) unnecessary potential failure points.

On another point;

The spigot/barb on the expansion tank has little clearance -  making the fitting of almost any security clamp on the tube, very difficult - I  double wrap  security wire before twisting (do not overtighten) - works extremely well

Use Viton/Tygon tubing that wont go hard and be sure to leave enough "slack" to accomodate engine movement😈

Speaking from personal experience, if you have a situation where the coolant overflows due to overheat or the pressure cap opening, the hot coolant will quickly fill the overflow bottle and any excess needs to be vented safely somewhere. You do not want it spraying all over your engine components.

Thanks everyone. Like others have said, the SeaRey assembly manual just calls for the tube to be inserted, but since the 914 IM calls for a fitting I thought I'd double check. It does make sense that if properly ziptied to the other tubes going near the overflow bottle it should not pull out, so that's what I'll go with.

And just one more thing sir, if you don't mind just one more thing. I measure the outlet from the expansion tank as 8.5 mm, just tried forcing a 1/4" hose on there, NFW, so I was thinking about using 5/16" instead. I don't see a size specified for this, only the it should be between 8-15 mm, so I think that would be Ok. 

TIA

Hi all

I would like to comment on the idea of a fitting so you can run fluids away from the engine fire zone.  First, antifreeze coolants are flammable.  They should never be able to dump out on to hot parts, like the exhaust, as they can cause other issues as well.  Think about hot fluids getting on the exhaust and causing smoke, it is not just fire that we have to worry about it.  The standard practice in aviation is to run all overflow lines out of the engine fire zone.  In a tractor this would be normally under the rear edge of the lower firewall.  In a pusher, such as the SeaRey noted, exit them below the exhaust and behind the engine as much as possible.  Open vents, the hole in the cap, are not aviation standard.  If you dont care do whatever you want, it's your experiment.  

You can reference standard practices in FAA AC-43-13 current addition.  You will find vents shown there.  It is also called out in any certified aircraft with fluids to vent in the build manuals.  The SeaRay is not certified so you can do what you want.  Just wanted to point out why Rotax calls for a vent tube to be used and not just a hole in the cap. 

Cheers