While there are some significant differences with which I am not familiar between the RTV900 and the RTV-X900 that I have... I thought I’d mention the problem I ran into similarly with my X900 cooling system.
I found a small leak beneath the drivers seat which proved to be where a rubber hose clamped to a metal pipe. I removed the clamp and cleaned corrosion off the pipe and reassembled things .... then went to refill the coolant. THAT’s where a problem developed:
I refilled the radiator and noticed the overflow reservoir was still full so I thought everything was OK. But. NOPE. It overheated very shortly and when I rechecked the radiator it’s tank was empty AND the overflow reservoir was also!
I had to add almost another half gallon and the reason I was puzzled was because prior to the work both were full, and I caught ALL the drained fluid and was able to pour it back in which gave the impression all was fine.
BUT... I did not know about a “vent hose” which is equipped with a plastic valve for the express purpose of venting air out of the system after it’s been opened for service.
If your system hasn’t been completely re-filled you’ll likely know it shortly because it will overheat. This can damage the head gasket and perhaps even crack a head...so immediately shut it down if it does overheat and let things cool off before opening/re-filling the system. I’ll try to find that other post where I showed the vent hose location and come back to edit this post with a link to it.
Here’s the thread:
http://www.nettractortalk.com/forums/showthread.php?t=17953