Coolant Leak?

If you've got a coolant temp sensor somewhere in the system, you could remove that and pressurise it there. Don't go mad with the pressure, just enough to detect some evidence of a leak.

Hi Brett,

Make sure not to over fill the reservoir tank. If it's a standard Rotax tank then 1/2 to 2/3 full is fine. If you over fill it then any incoming coolant from the engine has no place to go, but out the tank vent. If you're getting too much coolant from the expansion tank then you are either getting too hot or you might even need to replace the expansion tank cap,

Coolant leaks can sometimes be hard to find unless you know those hard to spot point because the in coming air flow from flying blows it off the leak point and makes it harder to find. The post from me above are two common points.

For the 17 mm hose you can squeeze them hard and if there is a leak you may see it ooze from under a hose end. If it's from the 90 degree fittings on top of each cylinder look for a tiny bit of residue around the tube where it goes into the flange that holds it in place.

My guess: nothing is leaking. A bad radiator cap will allow coolant to blow through the overflow line and out the top of the overflow bottle.

Worse, it will gradually pump a dangerous amount of the coolant out of the system, all while leaving a goodly amount in the plastic overflow bottle.

The level which counts is the level in the expansion tank spider on top of the engine. It should be filled to the edge of the brass flange that the lower cap rubber is supposed to seal against. This is also the only proper place to fill the system.

I didn't lean to much on the cap since it was just 25 hours old, but you never know it could be.

Thanks for the additional responses and based on those responses I will do a coolant system pressure that includes the thermostat.

Section 05-50-00 of Maintenance Manual Line specifies the Rotax procedure for doing this.  

I have a couple of questions regarding this procedure:

 - Is there an alternative to having to purchase a meter of 17 mm ID coolant hose part # 922 250?  It seems like an expensive way to get the needed few inches of hose.

 - Why does figure 5.19 specify that the plug that is to seal off the open end of the hose is to have a 12 -13 mm diameter?  Isn’t that too small to seal the 17 mm ID of the hose?

- Is using the coolant temperature sensor hole in the cylinder head an alternative?  If so, what is thread specification of this hole?

Many thanks for your assistance.

Brett