By design, the system is self purging. The amount of coolant added to the plastic reservoir, provided it is visible, does not matter. The coolant level, as you indicated, would be adjusted upon reaching normal temps.

Not that long ago I replaced the combined assembly of water pump with integrated thermostat. The fault I noticed was randomly, temp would be normal, then start indicating higher than normal, then return to normal, and other times the gage would simply fluctuate.

Replaced the water pump / thermostat assembly, and issues resolved. Easy repair to replace the water pump assembly, just was stupid expensive for the part, I mail ordered from a nearby dealer, actually my dealer of choice, since their parts department had the item in stock.

 

Maybe an air lock? Often on marine diesel engines we work on we will get air locks. We keep the cap off, and add coolant directly, not to the recovery bottle.
I do not know about these Rotax engines, but you will see the coolant flowing when looking in the radiator. If there is an air lock or a coolant pump failure you will not see the coolant flowing.

 

All the best with it. Though it sure acts like a typical thermostat failure on the 1330.

As mentioned, ours started doing odd stuff. No amount of love made it better. Replaced assembly, filled with coolant. No bleeding, or purging aside from simply filling.

The thermostat can be removed. Assembly must be on bench. Then with great care not to break the thermoplastic waterpump housing, the tangs can displaced, allowing removal of the thermostat housing and thermostat itself.

Pretty sure, prior to getting banned from Spyderlovers, I posted this info with photos. The thermostat is not a typical item and is proprietary to the assembly. Nothing matches up.

Also, while you might consider using a typical style, it can fit. However, the oem type is a bypass style thermostat.

I considered installing an inline thermostat. Even purchased all the needed parts. Unfortuately, if the thermostat is removed, the bypass feature is removed also. Doing this will result in overtemp as the coolant only circulates within the engine.

Again, all the best with it.

 

It just seems odd that it worked fine the 3 times I flushed it with water, but not the final time with coolant.

I plan to overfill it today and see if it will prime.
I never had cooling problems before, so I doubt the pump or thermostat failed at this particular moment.

Thanks

 

If the thermostat has easy access it is simple to check its function with a pot of hot water. you probably know this

 

Yes. I added another pint of coolant mix, jacked up the front and tried again.
The temp came up rapidly and it still didn't circulate, so I loosened the bleed screw on the front of the block, letting out a couple ounces of coolant.
I restarted it, and the temp came up normally, with the radiators getting flow at around 170 degrees.

Hope this helps others in the future. The bleed screw seems to be the trick. 👍

 

Yep... Bleed screws all over a marine diesel