I overheated the 99 RMK 700 last time out at the end of a full day of riding. The temp light came on, I pulled over, the coolant was totally full and pressurized, but the heat exchangers were ice cold and packed with snow. So I lost circulation somehow. The head is definitely warped, but before I fix the engine I need to figure out what happened with the coolant. I'll pull off the thermostat first, but I think it's pretty unlikely that it would get stuck shut after being open all day.

The next step will be check the water pump drive belt, and I don't know how to do that. It looks like you have to remove the recoil starter housing. But, the starter housing has the oil pump attached to it, and I don't know if there is any trick to removing any of this stuff. So I'm looking for guidance from anyone who knows. I believe its the same as the xc700 if that helps.

How will I know if the water pump is bad? I've seen dozens of car water pumps go bad and they always leak. Mine is not leaking. If the pump is not seized and not leaking, is there any other way for me to know if it's working? I suppose remove it and test the manual way? Thanks in advance

:nuke:

You might pull the hose, or a hose, from the pressure side of the pump and see if pulling the engine over has any effect. I am only passingly familiar with that engine so can't give any specifics on taking things off. I would only be making a guess but think you could disconnect the oil lines from the pump and remove the cover, bleeding things when you put it back together.

Yeah I guess I'm just going to dig in and see what happens. But I just know I'm going to break something. Might be a good idea to run a tank of maybe 60:1 premix after all the work is done. I don't really expect to ride it again this year, don't really need the 151" track for slush riding anyway. What I will miss is the power, there is such a huge difference between the piped 700 of the RMK and the 600 single in my Vmax. What I won't miss is the insanely bad fuel mileage. I'll also enjoy what now feels like a short track to me, the 136" sleds. I've learned to handle that big track and it allows you to do amazing things, but man is it a burden at times.

I just met an older guy who is serious motorhead. Although he has never snowmobiled, he knew a lot about 2 strokes. He said with engines that constantly run at high rpms, you can get coolant electrolysis. It's more likely to happen at higher coolant to water ratios, which again should make snowmobiles especially vulnerable. Basically your coolant becomes too conductive as it gets old and as a result the DC current runs through things like your coolant impeller and in pretty short time eats them away till they fail. He said this can happen in just a few years. At any rate, we agreed that the belt is most likely the problem, or it could just be seized up. I'll probably open it up Wednesday and have my answers.

Okay - it's apparently a water pump bearing. The thing kinda turns, but it's rough and uneven and you can wiggle it around pretty easy.

Next thing will be figuring out the extent of what happened to the engine. The same belt that drives the water pump also drive the oiler, so for at least a little while it was running without oil as well. I don't intend to fully tear it down and check it over, just basically figure out what I need to do with the head and then get it fixed and cross my fingers.

Looks like it's possible to replace the bearings in this thing, and it looks like I just have to replace the bearing and make sure nothing else is broken.

unless the belt was broken your water pump will still pump with a bad bearing. you can test your thermostat in a pan filled with water on the stove. should open at 160.